ijC_€7^-^- 


Issued  July  17,  1908. 


Si  U.  S.  DEPARTMENT  OF  AGRICULTURE, 


BUREAU  OF  ANIMAL  INDUSTRY.— Bulletin  107. 

A.  D.  MELVIN,  <Jhief  op  Bureau. 


IHb  ANALYSIS  OF  COAL-TAR  CREOSOTE 
AND  CRESYLIC  ACID  SHEEP  DIPS. 


BY 


ROBERT  M.  CHAPIN, 

Assistant  Chemist,  Biochemic  Division. 


fornia 
mal 

■ty 


WASHINGTON: 

GOVERNMENT   PRINTING   OFFICE. 
19Q8. 


Issued  July  17,  1908. 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY.— Bulletin   107. 

A.  D.  MELVIN,  Chief  of  Bureau. 


THE  ANALYSIS  OF  COAL-TAR  CREOSOTE 
AND  CRESYLIC  ACID  SHEEP  DIPS. 


BY 


ROBERT  M.  CHAPIN, 

Assistant  Chemist,  Biochetnic  Division. 


WASHINGTON: 

GOVERNMENT   PRINTING   OFFICE, 
1908. 


THE  BUREAU  OF  ANIMAL  INDUSTRY. 


Chief:  A.  D.  Melvin. 

A.sniatant  Chief:  A.  M.  Farbinoton. 

Chief  Clerk:  E.  B.  Jones. 

Biochcmic  Division:  M.  Dorset,  chief;  James  A.  Emery,  assistant  chief. 

Dairy  Division:  Ed.  H.  Webster,  chief;  C.  B.  Lane,  assistant  chief. 

Inspection  Division:  Kice  P.  Steddom,  chief;  Morris  Wooden,  R.  A.  Ramsay, 
and  Albert  E.  Behnke,  associate  chiefs. 

Pathological  Division:  John  R.  Mohler,  chief;  Henry  J.  Washburn,  assist- 
ant chief. 

Quarantine  Division:  Richard  W.  Hickman,  chief. 

Division  of  Zoology:  B.  H.  Ransom,  chief. 

Experiment  Station:  E.  C.  Schroeder,  superintendent ;  W.  E.  Cotton,  assistant. 

Animal  Husbandman:  George  M.  Rommel. 

Editor:  James  M.  Pickens. 

BIOCHEMIC  DIVISION. 

Chief:  M.  Dorset. 

Assistant  chief:  James  A.  Emery. 

Meat  inspection  laboratories:  Central  laboratory,  T.  M.  Price  In  charge;  R.  H. 
Kerr,  Philli)  Castleman,  E.  H.  Ingersoll,  R.  R.  Henley,  E.  J.  Ralph,  J.  N.  Taylor, 
W.  B.  Meyer,  H.  I.  Littlejohn,  assistants.  Chemists  In  branch  laboratories: 
Ralph  Hoagland,  A.  E.  Graham,  C.  H.  Swanger,  A.  H.  Roop,  W.  B.  Smith, 
E.  A.  Boyer,  Clarence  T.  N.  Marsh,  W.  P.  Colvln,  W.  C.  Powlck,  J.  B.  Munroe. 

Hog  cholera  investigations:  In  charge  of  Chief  of  Division;  C.  N.  McBryde, 
bacteriologist;  W.  B.  Nlles,  Inspector  In  charge  of  field  experiments;  H  J.  Shore, 
assistant  bacteriologist. 

bacteriological  investigations  of  meat  food  products:  C.  N.  McBryde,  bacteri- 
ologist in  charge. 

Investigations  of  animal  dips:  Robert  M.  Chapin,  In  charge;  A.  V.  Fuller, 
assistant. 

Investigations  of  disinfectants:  Frank  W.  Tllley,  bacteriologist. 

Preparation  of  tuberculin  and  mallein:  In  charge  of  Chief  of  Division;  A.  M. 
West  and  H.  J.  Shore,  assistant  bacteriologists;  W.  S.  Stamper,  H.  S.  McAuley, 
Roy  E.  Burnett,  assistants. 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Animal  Industry, 

Washington,  D.  C,  April  13,  1908. 

SiK :  I  have  the  honor  to  transmit  herewith  and  to  recommend  for 
publication  as  a  bulletin  of  this  Bureau  the  accompanying  manuscript 
entitled  "  The  Analysis  of  Coal-tar  Creosote  and  Cresylic  Acid  Sheep 
Dips,"  by  Robert  M.  Chapin,  assistant  chemist  in  the  Biochemic 
Division. 

The  Department,  in  accordance  with  Bureau  of  Animal  Industry 
Order  143,  sanctions  the  use  of  certain  classes  of  preparations  for  the 
official  dipping  of  sheep  and  cattle.  A  large  number  of  dips  are 
manufactured  and  used  throughout  the  country,  and  samples  are  con- 
stantly being  submitted  to  the  Department  for  the  purpose  of  having 
their  use  permitted  in  official  dipping,  the  analytical  work  as  a  basis 
for  passing  on  them  being  performed  in  the  Biochemic  Division  of 
this  Bureau. 

This  paper  deals  with  methods  of  determining  the  various  constit- 
uents of  dips  prepared  from  coal-tar  derivatives.  It  has  become  of 
some  importance  to  find  methods  of  analysis  which  shall  be  sufficiently 
accurate  and  at  the  same  time  not  make  excessive  demands  upon  the 
skill  or  time  of  the  analyst,  and  the  methods  proposed  in  the  paper 
appear  to  be  comparatively  simple  and  considerably  more  accurate 
than  those  heretofore  employed.  They  should  accordingly  be  useful 
to  persons  concerned  in  the  examination  and  production  of  such  dips, 
and  are  expected  to  assist  manufacturers  in  meeting  the  Department's 
requirements. 

Respectfully,  A.  D.  !Melvin, 

Chief  of  Bureau. 

Hon.  James  Wilson, 

Secretary  of  Agriculture.  _ 


Digitized  by  tine  Internet  Arciiive 

in  2007  witii  funding  from 

IVIicrosoft  Corporation 


littp://www.arcliive.org/details/analysisofcoaltaOOcliapiala 


CONTENTS. 


Page. 

Introductory 7 

Coal-tar  creosote  dips 7 

Current  methods  of  analysis 8 

Criticism  of  methods 9 

Method  of  analysis  adopted  by  the  Bureau 10 

Determination  of  water 10 

Determination  of  soda  and  pyridin  bases 11 

Determination  of  phenols 13 

Determination  of  rosin  acids 17 

Determination  of  occasional  ingredients 20 

Cresylic  acid  dips 21 

Method  of  analysis  adopted  by  the  Bureau 22 

Determination  of  water 22 

Determination  of  potash  (or  soda)  and  pyridin 22 

Determination  of  phenols 22 

Determination  of  rosin  or  fatty  acids 22 

Analysis  of  coal-tar  oils  and  commercial  cresylic  acid 24 

Calculation  of  proper  dilution  of  dips 25 

Coal-tar  creosote  dips 25 

Cresylic  acid  dips 27 

Experimental  work  with  methods  of  analysis 27 

Determination  of  phenols 27 

Tests  with  coal-tar  creosote  dips  of  known  composition 30 

Test  with  cresylic  acid  dip  of  known  composition 32 

Tests  for  nonvolatile  acid  bodies  in  coal-tar  creosote  and  commercial 

cresylic  acid 33 

Summary 35 


LLUSTRATION. 


Page. 
Figure  1.  Tube  for  measuring  phenols 16 


THE  ANALYSIS  OF  COAL-TAR  CREOSOTE  AND  CRESYLIC 
ACID  SHEEP  DIPS. 


INTRODUCTORY. 

The  Department  of  Agriculture  at  present  sanctions  the  use  of 
properly  constituted  coal-tar  creosote  and  cresylic  acid  preparations, 
commonly  termed  "  dips."  for  the  official  dipping  of  sheep  for  the 
cure  of  scabies.  The  proprietor  of  each  dip  must,  however,  fulfill 
certain  requirements  in  order  that  the  use  of  his  product  may  be 
permitted  in  official  dipping,  involving  the  submission  of  a  sample 
to  the  Dei^artment  for  examination."  The  Biochemic  Division  of 
the  Bureau  of  Animal  Industiy  has  accordingly  been  obliged  to 
examine  a  large  number  of  these  compounds  and  to  confront  the 
problem  of  finding  analytical  methods  of  considerable  accuracy 
which  would  yet  not  make  excessive  demands  upon  the  skill  or  time 
of  the  analyst.  While  these  substances  have,  of  coui'se,  afforded 
a  field  for  investigation  by  a  number  of  different  Avorkers.  so  far  as 
known  no  other  laboratory  has  been  compelled  to  make  their  detailed 
examination  such  a  matter  of  routine.  Accordingly  the  methods 
here  applied  may  be  of  interest  to  others  who  have  occasion  to 
examine  these  or  similar  compounds,  as  well  as  to  manufacturers. 

COAL-TAR  CREOSOTE  DIPS. 

These  dips  are  quite  simply  made  by  dissolving  rosin  in  phenol- 
bearing  coal-tar  oils,  adding  an  aqueous  solution  of  caustic  soda  and 
applying  a  moderate  degree  of  heat  until  saponification  is  complete. 
The  undiluted  dip  should  be  a  clear,  uniform  liquid,  showing  no 
separation  of  its  constituents.  When  properly  diluted  with  a  con- 
siderable quantity  of  water  there  results  a  permanent,  uniform  emul- 
sion, from  which,  on  standing,  no  oily  layer  or  globules  should 
separate  either  at  top  or  bottom. 

The  completed  dip  will  contain,  then,  the  following  substances: 
(1)  Coal-tar  hydrocarbons,  (2)  phenols,  (8)  pyridin  and  other  vola- 
tile bases  contained  in  coal-tar  oils,  (4)  rosin  acids,  (5)  soda  (XaoO), 
(G)  water.  In  special  cases  certain  other  substances  may  be  looked 
for.     The  rosin  acids  and  soda  will  be  present  in  approximatelj' 

"  Hureau  «)f  Animal  Industry  Order  143. 


8  ANALYSIS   OF   COAL-TAR   SHEEP  DIPS. 

equivalent  proportions  in  combination  as  a  rosin  soap.  To  the  latter 
sul)stancv  is  clue  the  power  of  the  dip  to  form  a  perfect  emulsion 
when  diluted  with  water. 

CURRENT  METHODS  OF  ANALYSIS. 

Methods  of  analysis  heretofore  employed  may  [ye  classified  into 
(a)   commercial  and    (b)   scientific. 

The  commercial  methods  aim  at  quick  results  and  assume  that  the 
hydrocarbons  antl  })henols  alone  need  be  determined,  since  they  are 
the  essential  Lnfjredients  of  the  dip.  A  measured  or  weighed  amount 
is  shaken  with  acjueous  sulphuric  acid,  the  separated  aqueous  layer  is 
run  otf,  and  the  residual  oily  portion  is  poured  into  a  fractionating 
flask  and  distilled  into  a  graduated  cylinder  until  rosin  begins  to 
decompose,  as  shown  by  the  character  of  the  vapors  and  the  distillate. 
The  distillate  will  then  supposedly  contain  all  the  phenols  and  all 
the  coal-tar  hydrocarbons  except  a  slight  amount  remaining  in  the 
flask,  which,  however,  is  in  a  measure  balanced  by  a  small  amount 
of  rosin  oil  in  the  distillate.  After  taking  the  volume  and  specific 
gravity  of  the  distillate  in  the  cylinder,  strong  aqueous  caustic  soda 
is  introduced ;  the  cylinder  is  then  stoppered  and  thoroughly  shaken. 
Phenols  will  be  taken  up  by  the  caustic  soda,  and  will  be  contained  in 
the  alkaline  aqueous  layer  which  separates  after  the  cylinder  has 
stood  some  time.  The  volume  of  hydrocarbons  in  the  amount  of  dip 
taken  may  theji  be  read  directly,  and  the  volume  of  phenols  may  be 
obtained  by  difference  or  by  noting  the  increase  in  volume  of  the  soda 
solution. 

The  process  undoubtedly  undergoes  some  modifications  in  the  hands 
of  different  workers,  but  the  foregoing  is  a  general  outlijie  of  a  class 
of  methods  which  are  apparently  used  considerably  by  commercial 
chemists,  judging  from  information  which  has  come  to  the  Biochemic 
Division  from  several  different  sources. 

The  scientific  methods  follow  in  general  the  system  given  by 
Allen."  Fifty  grams  of  dip  are  shaken  with  ether  and  aqueous  sul- 
phuric acid.  Bases  are  removed  in  the  aqueous  layer,  which  is  then 
treated  with  excess  of  sodium  hydroxid,  and  the  volatile  bases  are 
distilled  off  with  steam  and  determined  in  the  distillate  by  titration 
with  standard  acid  and  methyl  orange.  The  ethereal  portion  is 
shaken  with  aqueous  caustic  soda,  which  removes  phenols  and  rosin 
acids,  leaving  in  ethereal  solution  In^drocarbons  which  are  weighed 
after  expulsion  of  ether.  The  alkaline  aqueous  solution  of  phenols 
and  rosin  acids  is  acidified  with  sulphuric  acid,  and  the  phenols  are 
distilled  over  with  steam  and  determined  in  the  distillate  by  any  suit- 
able method.     The  distillation  flask  containing  the  rosin  acids  is 

"Allen,  A.  H.,  C'omiuercial  Organic  Analysis,  3d  ed.,  Vol.  II,  Pt.  II,  p.  262. 
lUOl. 


CRITICISM   OF   CURRENT   METHODS   OF   ANALYSIS.  9 

cooled,  the  rosin  acids  are  separated  by  ether  and,  after  expulsion  of 
ether,  weighed.  Soda  is  determined  by  ignition  of  a  small  portion 
of  the  dip  in  a  crucible,  either  to  sodium  carbonate  or,  with  addition 
of  sulphuric  acid,  to  sodium  sulphate. 

CRITICISM    OF    METHODS. 

The  commercial  method  of  analysis,  while  rapid,  contains  some 
serious  sources  of  error.  Obviously  a  little  of  the  phenols  is  lost  in 
the  acid  aqueous  extract.  Moreover,  practically  all  dips  contain 
more  or  less  voluminous  insoluble  carbonaceous  matter,  which  con- 
duces to  the  formation  of  an  emulsion  at  the  junction  of  the  two 
layers  in  the  separating  funnel.  Loss  of  hydrocarbons  and  phenols 
results  if  this  emulsion  is  run  off,  while  if  allowed  to  remain  with 
the  oily  layer,  water  together  with  sulphur  dioxid  or  hydrogen  sul- 
phid  will  pass  into  the  distillate,  all  of  which  tend  to  increase  un- 
duly the  volume  of  hydrocarbons  and  phenols  when  the  latter  are 
measured.  It  is  also  difficult  to  decide  exactly  when  to  stop  distilla- 
tion, particularly  in  those  dips  containing  oils  of  very  high  boiling 
point.  In  any  case  the  distillate  will  contain  some  rosin  oil,  while 
some  coal-tar  oil  will  be  left  behind  with  the  rosin,  the  relative 
amounts  of  which  will  vary  according  to  the  individual  judgment  of 
the  analyst  and  will  depend  to  a  considerable  extent  upon  the  char- 
acter and  proportions  of  rosin  and  coal-tar  oil  in  the  particular  dip 
under  examination. 

But  the  most  serious  source  of  error,  and  the  one  which  by  itself 
renders  the  method  utterly  untrustworthy,  is  the  fact  that  undecom- 
posed  rosin  is  distilled  along  with  the  hydrocarbons  and  phenols. 
This  rosin,  which  in  dips  containing  much  oil  of  high  boiling  point 
may  amount  to  several  grams,  is  of  course  taken  up  by  the  aqueous 
caustic  soda  with  which  the  distillate  is  shaken,  and  will  conse- 
quently cause  the  amount  of  phenols  to  appear  several  per  cent  too 
high.  Nor  is  the  presence  of  rosin  in  the  distillate  due  to  carrying 
the  distillation  too  far.  To  decide  this  point  dips  were  distilled  as 
described,  and  the  distillate  was  collected  in  six  to  eight  fractions. 
Each  fraction  was  treated  according  to  the  scientific  method  for  the 
separation  of  hydrocarbons,  phenols,  and  rosin.  The  results  showed 
that  rosin  began  to  come  over  soon  after  200°  C.  had  been  reached, 
and  continued  to  appear  in  increasing  quantity,  while  the  distillation 
of  phenols  is  certainly  not  complete  at  250°  C.  It  appears,  there- 
fore, utterly  useless  to  attempt  to  develop  any  accurate  method  of 
analysis  along  these  lines. 

The  .scientific  method,  though  far  superior  to  the  commercial  in 
accuracy,  possesses  numy  disadvantages.  As  is  well  known,  hydro- 
carbons are  considerably  soluble  in  aqueous  sodium  resinate  and 
sodium  cresylate,  while  both  of  these  latter  salts,  particularly  cresy- 
42557—08 2 


10  ANALYSIS   OF   COAL-TAR   SHEEP  DIPS. 

lates,  are  readily  hydrolyzed,  and  yield  notable  amounts  of  their 
acids  to  ether.  Hence  many  extractions  and  reextractions  are  neces- 
sary to  obtain  anything  like  a  complete  separation  of  hydrocarbons 
from  rosin  and  phenols,  and  the  process  requires  much  time  and 
much  ether.  Moreover,  it  is  often  impossible  to  obtain  a  satisfactory 
result  on  weighing  the  hydrocarbons  because  their  volatility  renders 
it  difficult  to  free  them  completely  from  ether  and  moisture  without 
undue  loss.  Many  dips  contain  a  certain  percentage  of  light  oils, 
and  obviously  results  may  then  be  far  from  the  truth.  Petroleum 
ether,  with  the  accompanied  use  of  alcohol,  offers  no  advantages  in 
the  operation  of  extraction,  and  renders  the  final  weight  of  hydro- 
carbons still  more  uncertain. 

METHOnS   OF   ANALYSIS   ADOPTED   BY    THE   BUREAU. 

In  deciding  upon  an  official  method  of  analysis  it  was  desirable  to 
adopt  one  that  would  not  depend  largely  upon  the  individual  judg- 
ment of  the  analyst,  but  would  give  definite  and  concordant  results 
when  the  same  sample  was  handled  by  different  operators,  and  these 
results  should  closely  approximate  the  truth.  It  is  evident  that  the 
scientific  method  just  referred  to  is  far  from  satisfactory  in  this  re- 
sjject.  It  is  also  evident  that  no  method  which  involves  separation 
of  the  hydrocarbons  and  the  determination  of  their  weight  can  yield 
results  fret'  from  suspicion.  For  the  other  ingredients  of  these  dips 
workable  methods  have  been  found  which  attain  reasonable  accuracy 
and  give  concordant  results  in  the  hands  of  any  chemist  of  ordinary 
ability  with  a  little  practice,  and  which  do  not  make  excessive  de- 
mands upon  time  nor  require  expensive  chemicals.  It  has  seemed 
best,  therefore,  to  determine  these  other  ingredients,  to  subtract  the 
total  of  the  percentages  so  obtained  from  100,  and  to  call  the  remain- 
der •'  hydrocarbons.'' 

The  following  methods  are  accordingly  those  now  employed  in  the 
laboratories  of  the  Biochemic  Division.  The  dip  is  well  shaken  be- 
fore weighing,  and  the  latter  operation  is  most  conveniently  per- 
formed by  pouring  into  a  beaker  somewhat  more  than  the  amount 
needed,  balancing  on  the  scales,  and  pouring  off  the  desired  amount 
into  the  receptacle  to  l)e  used  in  the  analysis. 

DKTEBMINATION    OF    WATER. 

Fifty  grams  of  dip  is  weighed  into  a  100  c.  c.  fractionating  flask 
with  a  moderately  high  side  tube,  beyond  the  exit  of  which  the  neck 
should  continue  for  not  more  than  one  inch,  and  the  flask  is  con- 
nected with  a  small  water-cooled  condenser  and  carefully  heated  with 
a  smoky  flame  until  oils  come  over  freely  and  carry  no  trace  of  water 
with  them,  but  the  distillation  should  not  be  unnecessarily  continued. 


METHODS   OF  ANALYSIS  ADOPTED  BY  THE  BUREAU.  11 

The  distillate  is  received  in  a  properly  graduated  25  c,  c.  cylinder, 
allowed  some  time  to  separate  completely,  and  the  volume  of  water 
read.  The  number  of  cubic  centimeters  of  water  multiplied  by  2 
equals  the  percentage  of  water.  Ordinarily  the  process  offers  no  diffi- 
culties. A  dip  extremely  high  in  rosin  may  bump  and  froth  over,  no 
matter  how  carefully  heated.  In  such  a  case  a  larger  flask  is  used, 
and  the  dip  is  diluted  with  about  an  equal  volume  of  water-free  min- 
eral or  coal-tar  oil.  In  case  separation  of  the  distillate  is  imperfect 
a  small  measured  amount  of  strong  XaCl  solution  is  added  from  a 
jjipette,  and  the  cylinder  is  nearly  filled  with  benzol,  shaken,  and  left 
at  rest  for  some  time.  The  volume  of  NaCl  solution  added  is  of 
course  to  be  deducted  when  the  reading  is  taken. 

DETERMINATION    OF    SOUA    AND    PYRIDIN    BASES. 

The  method,  which  is  a  novel  combination  and  adaptation  of  Avell- 
known  principles  and  processes,  depends  upon  the  fact  that  pyridin 
bases  are  alkaline  toward  method  orange,  but  not  toward  phenolphtha- 
lein.  A  known  weight  of  dip  is  shaken  in  a  separatory  funnel  with 
ether  and  water  to  which  a  known  amount  of  sulphuric  acid  has  been 
added.  Rosin  soap  is  thus  decomposed,  and  all  bases  contained  in 
the  dip  will  pass  as  sulphates  into  the  lower  acid  aqueous  layer  which 
soon  separates.  The  latter  is  quantitatively  removed,  and,  ignoring 
acid  salts  for  the  sake  of  simplicity,  will  contain  the  substances — 

(a)  (b)  (c) 

Stage  I.  Xa,80,.  H,80,.  (C,H,X),H,80,. 

If  methyl  orange  is  now  added  and  the  solution  titrated  to  neu- 
trality with  standard  caustic  soda  the  result  will  be — 

(a)  (b)  (c) 

Stage  11.  Na,SO,.  Na^SO,.  (C5H5N),H,SO,. 

If  next  phenolphthalein  is  added  and  titration  with  standard 
caustic  soda  continued  until  the  solution  is  neutral  to  that  indicator, 
the  final  condition  of  the  solution  will  be — 

(a)  (b)  (c) 

Stage  III.  Xa.SO,.  Xa.SO,.  Na.SO,.  C,H,X. 

Obviously  the  amount  of  caustic  soda  required  to  change  the  solu- 
tion from  Stage  II  to  Stage  III  will  be  a  measure  of  the  amount  of 
pyridin  present,  while  if  the  amount  of  caustic  soda  added  in  the 
whole  titration  is  subtracted  from  the  e<iuivalent  in  soda  of  the 
sulphuric  acid  originally  introduced  the  remainder  will  equal  the 
amount  of  soda  in  the  dip.  Briefly,  the  amount  of  soda  equivalent  to 
H2SO4  (c)  measures  pyridin;  soda  equivalent  to  H.^SO^  [(a-j-b-f-c)  — 


12  ANALYSIS   OF   COAL-TAR   SHEEP   DIPS. 

(b-|-o)  ]  is  the  soda  of  the  dip.  The  process  is  executed  in  the  follow- 
ing manner: 

Ten  trranis  of  dip  is  weighed  into  a  200  c.  c.  short-stemmed  separat- 
inir  funnel.  50  c.  c.  ether  added,  exactly  30  c.  c.  of  N/2  H.SOj  run 
in  from  a  burette  and  the  funnel  shaken.  The  lower  aqueous  layer, 
which  now  contains  the  bases,  is  drawn  off  completely,  together  with 
any  insoluble  carbonaceous  matter  which  may  appear  at  the  junction 
of  the  two  layei-s.  No  harm  is  done  if  a  small  amount  of  the  ethereal 
layer  accompanies  the  insoluble  matter  in  the  separation.  The 
ethereal  solution  remaining  in  the  funnel  is  next  washed  four  times 
with  water,  using  about  20  c.  c.  each  time.  In  the  first  of  these  wash- 
ings the  funnel  should  not-l)e  shaken,  but  the  water  should  be  drawn 
off  at  once,  the  object  being  to  wash  out  the  stem  of  the  funnel  and  so 
avoid  loss  of  a  little  acid  therein  contained. 

All  tlie  aqueous  extracts  are  united  and  heated  on  the  steam  bath 
for  expulsion  of  ether.  The  liquid  is  then  passed  through  a  wet  filter 
into  a  300  c.  c.  flask,  the  filter  washed  with  hot  water,  the  flask  cooled, 
filled  to  the  mark,  and  the  contents  exactly  divided  between  two  uni- 
form titrating  flasks  of  about  300  c.  c.  capacity.  To  one  of  these 
portions  add  methyl  orange,  then  N/2  NaOPI  till  the  red  tint  just 
disappears,  as  nearly  as  can  l^e  determined  by  comparison  with  the 
second  portion.  Then  add  one-tenth  or  two-tenths  of  a  cubic  centime- 
ter more  of  N/2  NaOH  to  make  sure  that  neutrality  has  been  reached, 
though  much  excess  must  be  avoided,  else  the  separation  of  higher 
pyridin  bases  will  render  the  solution  turbid. 

This  first  titration  is  not  quantitative,  but  merely  to  aflFord  a 
.standard  of  comparison,  b}'  the  aid  of  which  the  second  portion  is 
quantitativeh'  titrated  to  exact  neutrality,  after  the  addition  of  an 
equal  amount  of  methyl  orange.  The  number  of  cubic  centimeters  of 
N/2  NaOH  used  is  noted,  phenolphthalein  added,  and  the  titration 
continued  to  the  end  point  of  that  indicator.  To  obtain  the  per  cent 
of  NaoO  in  the  dip,  subtract  the  total  number  of  cubic  centimeters 
of  N/2  NaOH  used  in  the  whole  titration  of  the  second  portion  from 
15,  and  multiply  the  remainder  by  0.31.  To  obtain  the  per  cent  of 
volatile  bases  reckoned  as  pyridin,  multiply  the  number  of  cubic 
centimeters  of  N/2  NaOH  used  between  the  end  points  of  methyl 
orange  and  phenolphthalein  by  0.79.  The  only  difficulty  in  the 
method  is  the  determination  of  the  point  of  neutrality  toward  methyl 
orange,  but  a  proper  use  of  the  standard  of  comparison  will  satis- 
factoril}'^  overcome  this." 

"  Recent  work  has  indicated  that  the  coloring  matters  which  tend  to  interfere 
with  the  accurate  observation  of  the  end  ix)int  with  methyl  orange  may  be 
almost  entirely  removed  from  the  solution  by  the  use  of  animal  charcoal. 
Powdereil  animal  charcoal  is  digested  on  the  steam  bath  with  dilute  hydro- 
chloric acid  in  sufficient  quantity  to  decompose  and  dissolve  all  carbonates  and 


THE   DETERMINATION   OF   PHENOLS.  13 

Results  obtained  for  pyridin  run  between  0.05  and  0.1  per  cent 
higher  than  by  Allen's  method. 

DETERMINATION    OF    PHENOLS. 

The  regulations  of  the  Department  of  Agriculture  "  include  under 
the  designations  "  phenols,"  "  cresols,"  and  "  cresylic  acid  "  those 
phenols  whose  boiling  points  range  between  185°  C.  and  250°  C. 
Benzophenol,  or  pure  carbolic  acid,  having  a  boiling  point  of  182°  C., 
is  accordingly  excluded,  the  reason  for  such  distinction  being  that 
it  is  considerably  more  toxic  in  its  effect  upon  animals  than  the 
phenols  of  higher  boiling  points.  '  As  a  matter  of  fact  the  compara- 
tively high  market  value  of  pure  carbolic  acid  as  a  separate  product 
renders  unlikely  the  presence  of  more  than  traces  of  it  in  such  com- 
pounds. It  is  well  known  that  the  so-called  crude  carbolic  acid  of 
commerce  consists  almost  entirely  of  higher  phenols. 

There  are  but  few  methods  for  determining  phenols  which  have 
received  at  all  extended  application.  Of  these  the  only  direct  acidi- 
metric  method,  that  of  Bader,^  is  applicable  to  benzophenol  alone, 
and  hence  is  of  no  value  in  the  present  case.  A  direct  gravimetric 
deteiTnination,  in  addition  to  its  inherent  sources  of  error,  demands 
a  complete  separation  of  hydrocarbons  from  the  phenols.  So  also 
does  any  volumetric  method  based  upon  the  reaction  between  phenols 
and  bromin  or  iodin.  This  separation  of  hydrocarbons  from  phenols, 
as  noted  under  the  description  of  the  scientific  method  of  analysis, 
is  tedious  and  uncertain,  and  is  to  be  avoided  if  in  any  way  possible. 

There  will  appear,  then,  to  be  two  methods  practically  applicable 
in  the  present  case — the  method  of  Schryver,*"  by  which  the  phenols 
are  acted  upon  in  benzol  solution  by  sodamid  and  the  evolved  am- 
monia titrated,  and  the  German  method  of  measuring  the  increase  in 


phosphates  present,  theu  washed  with  hot  water  until  the  wash  water  is  free 
from  chlorids,  and  tinallj-  dried  and  powdered. 

In  the  course  of  an  analysis,  after  the  tiasli  containing  the  acid  extract  from 
the  dip  has  been  heated  upon  the  steam  batli  until  ether  has  l>een  completely 
expelled,  1  to  1.5  grams  of  the  i)urified  animal  charcoal  is  added,  and  the  llask, 
frequently  shaken,  is  left  upon  the  steam  bath  for  30  to  GO  minutes.  The 
contents  are  then  filtered,  washed,  and  titrated  as  usual.  After  pr<)|)er  treat- 
ment with  animal  charcoal  in  this  manner  the  solution  will  be  a  pale  green  in 
color,  possessing  none  of  the  muddy  yellow  tint  which  tends  to  obscure  the  end 
point  with  methyl  orange. 

Expefiments  have  thus  far  failetl  to  show  that  any  inaccuracy  is  intrmluced 
into  the  u)ethod  by  the  use  of  animal  charcoal  in  the  manner  described. 

"Bureau  of  Animal  Industry  Order  143,  i).  is. 

'Zeitschrift  fiir  Analytisclie  Cliemie,  jahrg.  :n,  p.  .".S-«R>.     Wiesbaden,  1892. 

'^  Jotirnal  of  the  S<x'iety  of  Chemical  Industry,  vol.  18,  No.  G,  [k  i>')'.i-'trA>.  I>on- 
dou,  June  30,  1899. 


14  ANALYSIS   OF   COAL-TAR  SHEEP  DIPS. 

volume  of  a  caustic  soda  solution  when  the  phenols  are  absorbed  by  it. 
In  either  case  the  phenols  may  be  separated  from  interfering  sub- 
stances by  steam  distillation  of  the  acidified  dip.  Schryver's  method 
is  essentially  a  direct  determination  of  the  amount  of  phenol  hydroxyl 
j)resent,  and  the  actual  weight  must  be  obtained  through  a  knowledge 
of  the  mean  molecular  weight  derived  from  other  considerations. 
The  German  method,  on  the  other  hand,  is  a  measure  of  the  volume 
of  the  i)henols  when  in  solution  under  certain  conditions,  and  the  cor- 
responding weight  can  be  obtained  only  by  the  employment  of  an  em- 
pirical factor  or  coefficient  found  to  hold  true  for  that  particular 
kind  of  phenol  under  those  particular  conditions.  Since  in  both 
methods  a  certain  factor  must  be  somewhat  arbitrarily  adopted  by 
which  the  numbers  directly  obtained  are  to  be  multiplied  in  order  to 
obtain  the  weight  of  phenols  present,  and  since  the  possible  error 
thereby  involved  appears  of  about  the  same  magnitude  in  both,  that 
one  will  naturally  be  chosen  which  is  easiest  of  execution,  in  which 
respect  Schr^'ver's  method  is  at  a  decided  disadvantage. 

The  methods  of  procedure  which  considerable  experimental  work 
has  shown  to  be  satisfactory  is  as  follows : 

F'ifty  grams  of  dip  is  weighed  into  a  .500  c.  c.  round-bottomed  flask, 
20  c.  c.  of  1 : 3  HoSO^  is  added,  and  the  phenols  are  distilled  off  with 
steam.  The  flask  will  require  no  heating  if  a  rapid  current  of  steam 
is  passed  into  it,  but  may  with  advantage  be  packed  in  cotton  or  felt. 
Obviously  the  apparatus  must  be  so  set  up  and  the  distillation  so 
conducted  that  particles  of  rosin  may  not  be  mechanicalh'  carried 
over  by  the  current  of  steam.  Toward  the  end  of  the  distillation 
any  naphthalene  in  the  condenser  is  melted  out  bj'  shutting  off  the 
water  for  a  few  minutes,  or  if  separated  earlier  in  sufficient  quantity 
to  threaten  stoppage  of  the  condenser  tube,  distillation  is  interrupted 
while  hot  water  is  run  through  the  condenser.  The  distillate  is  re- 
ceived in  a  liter  flask  approximately  marked  for  each  100  c.  c.  capacity 
and  joined  to  the  condenser  by  a  cork  which  is  pierced  by  a  small 
glass  tube  connected  to  a  small  U  tube  containing  a  little  dilute 
caustic  soda.  The  latter  acts  as  a  trap  to  prevent  any  loss  of  the  dis- 
tilled phenols.  Distillation  is  continued  until  1  or  2  c.  c.  collected  in 
a  test  tul)e  gives  no  reaction  with  any  appropriate  reagent  for  phe- 
nols, such  as  ferric  chlorid.  A  volume  of  800  c.  c.  is  ample  in  nearly 
all  cases. 

A  supply  of  benzol  should  be  prepared  by  shaking  a  good  grade  of 
lienzol  with  dilute  sulphuric  acid,  then  with  dilute  caustic  soda  two 
or  three  times,  and  then  passing  through  a  dry  filter.  A  small  wash 
bottle  containing  some  of  this  benzol  will  be  found  very  useful  for 
rinsing  the  necks  of  separatory  funnels,  etc.  Of  this  purified  benzol 
150  c.  c.   is  measured   out  conveniently   at  hand,  the  contents  of 


THE  DETERMINATION    OF   PHENOLS.  15 

the  U  tube  and  5  c.  c.  of  1 : 1  HoSO^  are  added  to  the  distillate, 
and  the  latter  is  shaken  up  and  poured  into  a  separatory  funnel  of 
1,500  c.  c.  capacity,  the  flask  being  rinsed  out  with  successive  portions 
of  the  150  c.  c.  benzol.  When  all  is  in  the  funnel  25  grams  of  clean 
sodium  chlorid  is  added  for  each  100  c.  c.  of  distillate,  and  the  funnel 
is  well  shaken  for  five  minutes  and  left  at  rest  one-half  hour.  The 
aqueous  layer  is  then  run  off  slowly  and  completely,  the  funnel  being 
allowed  to  stand  until  there  is  no  further  separation.  The  benzol 
solution  of  phenols  and  hydrocarbons  is  transferred  to  a  500  c.  c. 
Erlenmeyer  flask,  while  the  aqueous  portion  is  poured  back  into  the 
separating  funnel  and  extracted  twice  more  in  the  same  way,  100  c.  c. 
of  benzol  being  used  each  time.  The  funnel  should  always  be  gently 
handled  after  the  aqueous  portion  has  been  drawn  off,  to  prevent  any 
impurities  from  the  sodium  chlorid  which  have  deposited  upon  its 
sides  from  becoming  mixed  with  the  benzol  solution.  The  three  ben- 
zol extracts  are  united  in  the  Erlenmeyer  flask,  15  c.  c.  of  pure  caustic 
soda  solution,  1 : 2,  is  added,  and  the  contents  of  the  flask  are  subjected 
to  a  rotatory  motion  for  some  time  in  order  that  the  phenols  may  be 
taken  up  by  the  caustic  soda  as  completely  as  possible. 

After  the  addition  of  a  few  grains  of  sand  the  flask  is  immersed  in 
a  water  bath,  connected  to  a  condenser,  and  all  but  40  to  50  c.  c.  of  the 
benzol  distilled  off.  With  the  aid  of  a  wash  bottle  containing  water 
and  provided  with  a  fine  jet,  only  a  small  portion  of  water  being  used 
at  a  time,  the  contents  of  the  flask  are  next  carefully  washed  into  a 
150  c.  c.  separatory  funnel.  With  proper  manipulation  the  flask 
should  be  completely  washed  when  the  volume  of  aqueous  portion  in 
the  separatory  funnel  amounts  to  not  more  than  50  c.  c.  Ten  cubic 
centimeters  of  strong  sulphuric  acid  (100  c.  c.  pure  concentrated 
HgSO^  to  120  c.  c.  water)  is  next  slowly  introduced  with  gentle  rota- 
tion of  the  funnel,  the  addition  of  acid  being  interrupted  and  the 
funnel  cooled  whenever  it  becomes  unpleasantly  warm  to  the  hand. 
Two  or  three  drops  of  methyl  orange  are  now  added;  and  if  on  mix- 
ing the  contents  of  the  funnel  the  lower  layer  does  not  acquire  a  pink 
color,  the  addition  of  acid  is  continued  until  acidity  is  assured.  Suffi- 
cient benzol  is  then  added  to  make  the  two  layers  in  the  funnel  ap- 
proximately equal  in  volume,  the  funnel  is  thoroughly  shaken  and, 
with  loosened  stopper,  left  at  rest  for  two  hours.  After  that  time 
the  aqueous  layer  is  slowly  and  completely  run  out,  the  analyst  mak- 
ing sure  that  on  longer  standing  no  more  will  drain  down  from  the 
sides  of  the  funnel.  The  benzol  solution  of  phenols  is  then  ready  to  be 
transferred  to  the  measuring  tube. 

The  measuring  tube  consists  of  a  glass-stoppered  pear-shaped  bulb 
of  about  100  c.  c.  capacity,  joined  at  its  tapering  end  to  a  tube  about 
1  foot  long  and  of  a  capacity  of  25  to  30  c.  c.     This  tube  is  accurately 


16 


ANALYSIS   OF   COAL-TAR   SHEEP  DIPS. 


gradiia 


ted  to  contain  25  c.  c.  at  20°  C.  in  divisions  of  one-tenth  c.  c. 
(See  fig.  1.) 

The  apparatus  is  cleaned  thoroughly  with 
soap  powder  and  hot  water,  and  dried,  best 
spontaneously,  though  alcohol  and  ether  may 
be  used  if  pure.  Perfect  cleanliness  is  essen- 
tial to  insure  a  proj^erly  shaped  meniscus. 
Between  15  and  16  c.  c.  of  caustic  soda  solu- 
tion, 1:3,  is  brought  into  the  tube  with  a 
l)ipette.  The  caustic  soda  should  not  be  al- 
h>wed  to  come  in  contact  with  the  interior 
of  the  bulb  or  the  upper  part  of  the  tube. 
After  a  few  moments  about  1  c.  c.  of  benzol 
is  added,  and  after  waiting  a  little  the 
height  to  the  top  of  the  now  almost  flat 
meniscus  is  noted.  The  benzol  solution  of 
phenols  is  next  transferred  from  the  separa- 
tory  funnel  to  the  tube,  care  being  used  to 
avoid  mixing  with  the  soda ;  the  separatory 
funnel  is  washed  out  with  a  little  benzol, 
which  is  also  transferred  to  the  tube,  and 
the  height  of  the  meniscus  is  again  noted. 
The  latter  may  often  be  obtained  more  accu- 
rately at  this  point.  The  tube  is  then  stop- 
pered, vigorously  shaken  for  three  minutes, 
and  set  aside  for  at  least  three  hours.  An  oc- 
casional rapid  rotation  of  the  tube  between 
the  palms  of  the  hands  will  insure  a  com- 
plete separation  of  the  layers.  Each  cubic 
centimeter  increase  in  volume  of  the  caustic 
soda  solution  may  be  taken  to  represent  one 
gram  of  phenols.  All  readings  of  the  tube 
should  be  taken  at  the  top  of  the  meniscus 
and  at  a  temperature  as  near  20°  C.  as  prac- 
ticable. 

This  method  of  treating  the  distilled  phe- 
nols is  essentially  that  of  Spalteholz," 
though  the  details  of  its  execution  were  not 
imparted  in  the  original  communication  and 
had  to  be  worked  out  independently.  A 
discussion  of  the  reasons  for  the  different 
steps  of  the  foregoing  process  will  be  entered 
into  in  a  later  section  which  deals  with  the 
experimental  work  done  (see  page  27). 


_25 


E2^ 


\22 


122 


EZl 


>Vsr~!?' 


yy 


Fig.  1.— Tube  for  measuring 
phenols. 


«  Cheuiiker-Zeitiing.  jahrg.  22,  no,  8,  pp.  58-59,  Ciithen.  Jan.  26,  1898. 


THE   DETEEMINATION    OF   ROSIN   ACIDS.  17 

From  certain  experiments  it  seems  possible  that  a  continuous  ex- 
traction apparatus  may  be  successfully  employed  to  extract  phenols 
from  the  aqueous  distillate  of  the  dip,  using  benzol  as  the  solvent, 
and  introducing  caustic  soda  solution  into  the  distillation  flask  of  the 
apparatus  at  the  beginning  of  the  operation  to  retain  the  extracted 
phenols.  A'^lien  the  extraction  is  completed  the  small  Jlask  of  the  ap- 
paratus will  contain  all  the  phenols,  dissolved  in  a  limited  amount  of 
caustic  soda  solution  and  overlaid  by  about  50  c.  c.  of  benzol.  The 
contents  of  the  flask  may  then  be  brought  readih^  and  completely  into 
a  separatory  funnel  and  acidified  in  the  usual  manner.  Certain  exi- 
gencies of  the  work  in  this  laboratory  have  rendered  somewhat  incon- 
venient at  the  present  time  a  practical  test  of  this  method  of  pro- 
cedure in  the  routine  examination  of  dips  submitted  for  analysis. 

DETERMINATION    OF    ROSIN    ACIDS, 

Resins  in  general  have  been  shown  to  contain  at  least  three  differ- 
ent classes  of  bodies:"  (1)  resin  acids  or  anhydrids,  (2)  esters  of 
these  or  similar  acids,  (3)  indifferent  neutral  bodies,  perhaps  hydro- 
carbons. Common  rosin,  or  colophony,  contains,  according  to  Allen,'' 
between  83.4  and  93.8  per  cent  of  free  rosin  acids  or  anhydrids.  The 
remaining  G  to  17  per  cent  consists  of  neutral  bodies,  soluble  in  ether 
and  not  extracted  from  ethereal  solution  by  aqueous  caustic  soda,  and 
accordingly  there  would  seem  to  be  no  practicable  means  of  distin- 
guishing and  separating  them  from  the  coal-tar  hydrocarbons  of  the 
dip.  Apparently,  then,  the  analyst  must  be  content  with  a  determina- 
tion of  the  amount  of  rosin  acids  present,  which  will  represent  about 
nine-tenths  of  the  amount  of  rosin  actually  used  in  manufacturing  the 
dip.    Either  a  gravimetric  or  a  volumetric  method  may  be  employed. 

Owing  to  the  degree  of  uncertainty  attached  to  the  exact  combining 
equivalent  of  the  rosin  acids  in  each  particular  dip,  the  gravimetric 
method  has  an  indubitable  advantage  in  point  of  accuracy  when 
properly  carried  out.  But  as  a  matter  of  fact  the  combining  equiva- 
lents of  a  considerable  number  of  rosin  acids  obtained  from  different 
dips  in  the  gravimetric  way  in  the  course  of  anahsis  have  been  found 
to  vary  very  little,  not  enough  in  any  case  to  cause  a  possible  error  of 
half  a  per  cent  in  the  analysis  of  a  dip  of  ordinar}'  constitution. 
Moreover,  in  view  of  the  difficulty  of  completeh'  separating  hydro- 
carbons from  rosin  acids,  as  is  necessary  in  the  gravimetric  method, 
it  is  probable  that  the  ordinary  analyst  without  considerable  practice 
in  this  particular  operation  will  obtain  quite  as  accurate  results  by 
the    volumetric   method    as   by    the   gravimetric.      Accordingly    the 

,.  . . * 

"Allen,  A.  H.,  Commercial  Organic  Analysis,  3<1  e«l,  rev.,  Vol.  II,  Pt.  Ill,  p. 
141.     1907. 
Md.,  p.  160. 

42557—08 3 


18  ANALYSIS   OF    COAL-TAR   SHEEP   DIPS. 

volumetric  method  would  seem  to  recommend  itself  for  use  in  ordi- 
nary routine  work  on  account  of  its  greater  rapidity,  simplicity,  and 
probable  equal  accuracy  under  ordinary  conditions,  while  the  gravi- 
metric method  may  l)e  reserved  for  dips  extremely  high  in  rosin  or  for 
a  confirmatory  method  in  special  cases. 

For  the  determination  of  rosin  acids  by  either  method  it  is  most 
advantageous  to  make  use  of  the  residue  left  in  the  distillation  flask 
after  the  determination  of  phenols.  From  this  residue  all  phenols 
and  a  large  part  of  the  hydrocarbons  have  been  removed,  hence  the 
necessary  extraction  by  ether  is  expedited.  After  cooling,  the  acjue- 
ous  portion  of  the  contents  of  the  flask  is  poured  into  a  separatory 
funnel,  with  as  little  rosin  as  possible,  and  extracted  Avith  ether. 
The  acjueous  portion  is  run  otf  and  discarded,  the  residue  in  the  flask 
is  completely  dissolved  and  brought  into  the  funnel  with  ether,  40 
to  50  c.  c.  of  water  is  added,  and  the  funnel  well  shaken.  The  pres- 
ence of  insoluble  carbonaceous  matter  will  usually  cause  a  persistent 
emulsion  at  the  junction  of  the  two  la3'ers,  which  may,  in  fact,  en- 
tirely fill  the  lower  part  of  the  funnel. 

This  is  wholly  run  oft*  into  a  300  c.  c.  Erlenmeyer  flask  and  the 
ethereal  solution  well  shaken  again  with  successive  portions  of  water, 
the  water  being  run  off  each  time  to  the  clear  ethereal  solution,  until 
the  carbonaceous  matter  is  wholly  removed  and  separation  takes 
place  in  the  funnel  quickly  and  cleanly.  These  wash  waters  are  all 
received  in  the  flask  containing  the  first  separated  emulsion,  and 
this  is  heated  upon  the  steam  bath  until  ether  is  expelled.  The  con- 
tents are  then  brought  more  or  less  completely  upon  a  Avet  filter  and 
washed  with  hot  water.     At  this  point  the  methods  diverge. 

Grarimetric  method. — In  case  the  gravimetric  method  is  to  be 
employed,  after  a  brief  washing  of  the  insoluble  carbonaceous  residue 
with  hot  water  both  flask  and  filter  are  well  drained.  Both  are  then 
washed,  first  with  a  little  absolute  alcohol  to  remove  water,  then  thor- 
oughly with  ether  until  all  rosin  is  dissolved  and  the  filtrate  comes 
through  colorless. 

The  united  ethereal  solution  of  hydrocarbons  and  rosin  is  now 
thoroughly  shaken  with  about  -40  c.  c.  of  15  per  cent  caustic  soda. 
On  separation  there  will  be  three  layers.  The  lowest  one  usually 
contains  very  little  rosin  soap,  and  consequently  holds  but  a  small 
amount  of  hydrocarbons.  It  is  best  run  off  and  washed  separately 
with  ether.  One  washing  will  usually  free  it  completely  from 
hydrocarbons. 

After  the  first  layer  has  been  thus  removed,  about  50  c.  c.  of  water 
is  added  to  the  funnel  and  the  latter  is  well  shaken.  The  lower  layer 
of  rosin  soap  is  run  oft"  and  followed  by  5  to  10  c.  c.  of  water  without 
shaking,  the  funnel  l)eing  given  only  a  gentle  rotatory  motion.  The 
remaining  ether  solution  of  hydrocarbons  is  Avashed  twice  Avith  20 


THE   DETERMINATION    OF    BOSIN    ACIDS.  19 

to  25  c.  c.  of  about  4  per  cent  caustic  soda  solution,  each  washing 
being  followed  by  a  little  water  as  before  described.  These  two 
washings  with  dilute  caustic  soda  are  kept  apart  and  not  added  to 
the  main  solution  of  rosin  soap. 

The  main  solution  of  rosin  soap  is  now  washed  in  a  separatory  fun- 
nel with  successive  portions  of  ether,  followed  through  each  time  by 
5  c.  c.  of  water,  as  at  first,  until  the  ether  is  left  nearly  colorless.  The 
ether  extracts  are  shaken  through  in  their  order  with  the  two  wash- 
ings of  dilute  caustic  soda  already  used,  and  a  third  if  needed,  each 
being  followed  with  a  few  cubic  centimeters  of  water. 

All  the  aqueous  extracts  are  united  in  a  porcelain  dish  or  casserole, 
which  should  be  not  more  than  half  filled  by  them,  and  are  evapo- 
rated on  the  steam  bath  until  ether  is  dissipated  and  the  volume  re- 
duced to  a  convenient  amount.  The  contents  of  the  dish  are  then 
transferred  to  a  separatory  funnel  with  the  aid  of  a  spatula  and  hot 
water;  strong  sulphuric  acid  is  added  to  decompose  all  rosin  soap, 
and  after  complete  cooling  the  rosin  acids  are  extracted  by  ether  and 
washed  with  water  till  free  from  sulphuric  acid.  The  ethereal  solu- 
tion is  brought  into  a  weighed  Erlenmeyer  flask  with  a  few  grains  of 
.>5and,  the  ether  is  distilled  off,  and  the  flask  is  heated  in  an  oven  at 
110°  C.  until  the  absence  of  frothing  on  rotation  shows  elimination 
of  water;  it  is  then  cooled  and  weighed. 

Vohimefric  method. — As  alread}'  noted,  the  volumetric  method 
proceeds  identically  with  the  gravimetric  to  the  point  where  carbona- 
ceous matter  is  brought  upon  the  filter  and  washed  with  hot  water. 
The  washing  in  this  case  must  be  continued  until  the  wash  water 
comes  through  entirely  free  from  acid  reaction.  The  main  ethereal 
solution  has  meanwhile  been  brought  into  a  flask  and  the  ether  dis- 
tilled off.  The  filter  funnel  is  set  in  the  neck  of  this  flask,  and  the 
carbonaceous  matter  is  washed  with  hot  alcohol  previously  rendered 
neutral  to  phenolphthalein,  until  freed  from  rosin.  The  alcoholic 
solution  of  rosin  is  brought  into  a  graduated  flask,  and  an  aliquot 
part,  usually  one-fourth,  taken  for  titration  with  half-normal  caustic 
soda.  The  titration  is  conveniently  carried  out  in  a  200  c.  c.  Erlen- 
meyer flask  in  a  volume  of  100  to  125  c.  c,  the  portion  taken  being 
diluted  with  neutralized  alcohol  to  that  amount. 

Owing  to  the  very  dark  color  of  the  liquid  an  external  indicator  is 
necessary.  For  this  purpose  alkali  blue  is  best  adapted.  A  few  droj)s 
of  a  strong  alcoholic  stock  solution  are  added  to  25  or  30  c.  c.  of 
alcohol,  which  is  then  carefully  neutralized  with  tenth-normal  caustic 
soda.  Enough  alkali  blue  should  be  added  to  produce  a  deep  color, 
almost  a  cherry,  wlien  neutralized,  with  no  trace  of  violet.  This 
dilute  indicator  should  be  freshly  prepared.  A  supply  of  small  test 
tubes  8  to  10  millimeters  in  diameter  and  GO  to  80  millimeters  long 
should  be  at  hand,  cleaned  and  dried.     When  a  test  of  the  progress 


20  ANALYSIS   OF   COAL-TAR   SHEEP   DIPS. 

of  the  titration  is  to  be  made  about  ^  c.  c.  of  prepared  indicator  is 
poured  into  one  of  these  test  tubes,  and  to  this  is  added  a  drop  of  the 
liquid  under  titration.  If  a  violet  color  appears,  the  solution  still 
contains  free  rosin  acid,  and  more  N/2  XaOH  must  be  added  and  the 
solution  again  tested  with  a  fresh  tube  of  indicator.  If  the  indicator 
does  not  show  a  violet  color  upon  the  addition  of  one  drop  of  the 
li<iuid  under  titration,  addition  of  the  latter  is  continued  drop  by 
drop  until  an  amount  has  been  added  approximately  equal  in  volume 
to  the  amount  of  indicator  originally  in  the  tul)e.  i.  e.,  \  c.  c.  The 
continued  absence  of  a  violet  color  after  the  addition  of  this  amount 
indicates  that  the  solution  is  either  neutral  or  alkaline.  The  end  of 
the  titration  then  is  reached  when  a  greenish  or  violet  tint  just  fails 
to  appear.  A  fresh  tube  of  indicator  must  be  used  for  each  test.  It 
is  best  to  proceed  by  running  in  12  to  15  c.  c.  of  half-normal  caustic 
soda  at  once,  testing  and  continuing  addition  if  necessary',  a  cubic 
centimeter  at  a  time,  until  the  indicator  shows  alkalinity,  then  run- 
ning back  with  half-normal  hydrochloric  acid,  using  perhaps  0.4  c.  c. 
at  a  time  till  acidit)"  is  shown,  and  now  working  carefully  with  half- 
normal  caustic  soda  to  exact  neutrality.  One  cubic  centimeter  of 
half-normal  caustic  soda  is  considered  to  be  equivalent  to  0.162  gram 
of  rosin  acids. 

Phenolphthalein  may  also  be  used  as  an  indicator  in  a  similar  way, 
bv  preparing  an  alcoholic  solution  of  quite  a  deep  rose  tint.  The 
end  point  of  the  titration  will  then  be  reached  when  the  indicator, 
used  in  the  same  way  as  alkali  blue,  is  no  longer  bleached  by  the  addi- 
tion of  the  liquid  under  titration.  The  color  change  is  not  so  marked 
as  in  the  case  of  alkali  blue,  and  consequently  the  end  point  is  not  so 
sharp,  though  almost  equally  good  results  may  be  obtained  with  a 
little  care  and  practice. 

All  alcoholic  solutions  should  be  kept  from  contact  with  air  as  far 
as  possible  to  prevent  absorption  of  carbon  dioxid. 

DETERMINATION    OF    OCCASIONAL    INGREDIENTS. 

Liffht  oils. — The  presence  of  light  oils  will  usually  be  indicated  by 
the  relative  proportions  of  oil  and  water  which  come  over  in  the  early 
stages  of  the  process  of  distilling  the  dip  for  the  determination  of 
water.  The  odor  of  the  distillate  should  be  noted  at  this  point,  to 
identify  if  possible  the  nature  of  the  light  oils  present.  If  more 
information  is  desired,  about  150  grams  of  dip  is  thoroughly  shaken 
with  20  to  25  c.  c.  of  1 : 3  sulphuric  acid,  allowed  some  hours  to  sepa- 
rate, and  a  weight  of  oils,  etc.,  equivalent  to  100  grams  of  dip — i.  e.,  a 
weight  in  grams  equal  to  the  sum  of  the  percentages  of  hydrocarbons, 
phenols,  and  rosin — is  distilled  from  an  Engel  flask  fitted  with  a 
thermometer  until  the  temperature  reaches  180°  C.  The  distillate 
is  measured  and  further  examined  in  any  way  desired. 


ANALYSIS   OF   CRESYLIC   ACID  DIPS.  21 

Naphthalene. — Too  large  a  proportion  of  naphthalene  or  other  solid 
hydrocarbons  is  undesirable  on  account  of  the  liability  of  these  bodies 
to  separate  from  the  dip  in  freezing  weather  and  remain  for  a  long 
time  as  an  undissolved  sediment.  For  an  approximate  determination 
of  the  amount  of  solid  hydrocarbons  present  50  grams  of  dip  is  acidi- 
fied with  a  little  concentrated  hydrochloric  acid,  100  c.  c.  alcohol  added, 
and  the  containing  vessel  immersed  in  a  freezing  mixture  for  two 
hours,  with  occasional  stirring.  The  separated  hydrocarbons  are 
then  filtered  off  on  a  Buchner  funnel  or  plate,  washed  somewhat  with 
chilled  alcohol,  well  drained,  and  pressed  out  in  a  letterpress  between 
several  thicknesses  of  filter  paper.  The  mass  may  then  be  weighed 
and  subjected  to  any  further  examination  desired.  A  more  practi- 
cal test  is  to  subject  a  portion  of  the  dip  itself  to  a  temperature  of 
0°  C.  for  about  three  hours,  with  occasional  shaking  or  stirring.  It 
should  remain  perfectly  clear  and  liquid  and  show  no  separation  of 
solid  matter. 

Foreign  oils  and  creosotes. — By  the  regulations  of  the  Secretary  of 
Agriculture"  the  degree  of  dilution  which  may  be  accorded  to  a 
coal-tar  creosote  dip  is  explicitly  made  to  depend  upon  the  percent- 
ages of  coal-tar  oils  and  cresylic  acid  contained  in  the  dip.  Accord- 
ingly in  the  standardization  of  dips  for  official  use,  within  the  scope 
of  the  regulations,  petroleum  oil,  rosin  oil,  or  creosotes  of  other  origin 
than  coal-tar  must  be  regarded  as  extraneous  substances.  Investiga- 
tions are  now  in  progress  to  find  satisfactory  methods  for  detecting 
and  estimating  these  substances  when  present  in  dips.  At  the  present 
time,  however,  this  line  of  work  has  not  reached  a  point  of  develop- 
ment which  warrants  the  publication  of  any  results. 

CRESYLIC  ACID  DIPS. 

Cresylic  acid  or  cresol  dips  in  composition  approximate  more  or  less 
closely  the  "  liquor  cresolis  compositus  "  of  the  United  States  Pharma- 
copoeia, eighth  revision,  1905,  being  made  from  a  potash-linseed  oil 
soap  and  cresylic  acid  comparatively  free  from  hydrocarbons.  A 
properly  prepared  dip  of  this  character  should  upon  dilution  in  100 
parts  of  distilled  water  yield  a  practically  water-clear  solution,  show- 
ing absence  of  any  notable  amount  of  hydrocarbons  or  unsaponified 
oil.  On  dilution,  however,  with  hard  water  there  will  naturally  be 
sf>me  turbidity,  caused  by  the  precipitation  of  soap.  A  portion  of  the 
dip  when  treated  with  successive  small  portions  of  water  should  show 
itself  miscible  in  all  proportions.  At  no  stage  hhould  there  l)e  any 
notable  turbidity  or  separation  of  heavy  oily  globules  of  cresylic  acid 
due  to  absence  of  sufficient  soap. 

<"  Bureau  of  Aulnial   Imlustry  OrcU'r  14.'5,  p.  18. 


22  ANALYSIS  OP  COAL-TAR  SHEEP  DIPS. 

METHODS  or  ANALYSIS  AIX)PTED  BY  THE  BUREAU. 

The  methods  of  analysis  adopted  are  essentially  the  same  as  for 
coal-tar  tivosote  dips,  modified  in  details  to  suit  the  somewhat  dif- 
ferent composition  of  the  substances. 

UETEBMINATION   OF    WATER. 

The  distillate  must  always  be  received  in  a  stoppered  cylinder  and 
treated  with  benzol  and  sodium  chlorid  solution  as  described.  The 
results  will  be  about  0.5  per  cent  too  low.  The  addition  of  toluene  or 
a  similar  hydro<'arbon  to  the  dip  before  distillation  might  possibly 
improve  the  results. 

DICTEBMINATION    OF   POTASH     (OB    SODA)     AND    PYBIDIN. 

A  preliminary  test  is  here  necessary  to  determine  whether  potash  or 
.soda  is  the  alkali  present.  The  test  may  be  conveniently  made  by 
shaking  about  10  grams  of  dip  with  ether  and  a  little  dilute  hydro- 
chloric acid,  drawing  off  the  aqueous  layer,  and  applying  the  flame 
test  with  a  platinum  wire,  supplementing  this  with  any  other  con- 
firmatory test  necessary  or  desirable.  If  potash  is  found  to  be  the 
alkali  present  the  factor  0.471  must  be  used  in  place  of  the  factor  0.31 
employed  in  the  case  of  soda. 

DETERMINATION  OF  PHENOLS. 

Since  the  percentage  of  phenols  will  here  he  much  higher  than  in 
coal-tar  creosote  dips,  a  smaller  amount  of  dip  must  be  taken  for 
analysis,  usually  15  to  20  grams.  The  amount  should  be  as  large  as 
possible,  in  order  that  the  greatest  quantity  of  phenols  within  the 
capacity  of  the  tube  may  l)e  brought  to  measurement.  A  new  oppor- 
tunity for  error  is  here  afforded.  Linseed  oil  possesses  a  low  Reichert- 
Meissl  number,  00  to  1.43."  This  means  that  a  small  amount  of  vola- 
tile fatty  acid  will  accompany  the  phenols  through  the  stages  of  the 
process  and  tend  to  cause  too  high  results.  To  determine  the  possi- 
ble amount  of  this  error  25  grams  of  linseed  oil  was  saponified,  then 
acidified,  and  distilled  with  steam  until  800  c.  c.  had  been  collected. 
The  distillate  was  treated  by  the  regular  method  and  an  increase  in 
volume  between  0.02  and  0.07  c.  c.  observed.  In  view  of  the  fact  that 
this  (juantity  of  soap  is  four  or  five  times  as  much  as  would  be  present 
in  an  ordinary  analysis,  the  error  which  is  likely  to  arise  from  this 
source  would  apjjear  negligible. 

DETEBMINATION    OF    ROSIN    OR   FATTY    ACIDS. 

The  odor  of  the  dip  itself,  and  more  especially  the  character  of  the 
residue  left  in  the  flask  after  the  distillation  of  phenols,  will  inform 

*  Hopkins's  Oil  Chemists'  Handbook,  page  38. 


DETERMINATION   OF   ROSIN   IN   CRESYLIC   ACID   DIPS.  23 

the  analyst  whether  rosin  or  fatty  acids  are  to  be  determined.  Rosin 
will  collect  in  a  solid,  hard  button  at  the  bottom,  while  fatty  acids 
will  form  a  liquid  oily  layer  floating  upon  the  surface  of  the  aqueous 
contents.  In  either  case  the  whole  is  extracted  with  ether,  washed 
Avith  water,  and,  after  evaporation  of  ether,  dissolved  in  neutralized 
alcohol  and  titrated  with  half-normal  caustic  soda.  One  cubic  cen- 
timeter of  half-normal  soda  will  represent  0.138  gram  fatty  acid 
anhydrids"  and  0.015344  gram  glycerin.  Cresol  dips  containing 
rosin  soap  are  not  at  present  permitted  in  official  dipping. 

Such  a  detailed  analysis  of  a  cresol  dip  would  appear,  however, 
seldom  necessary.  Phenols  must  of  course  be  determined  as  accu- 
rately as  possible.  An  examination  of  the  odor  and  appearance  of 
the  residue  left  in  the  flask  after  distillation  of  phenols  will  indicate 
the  character  of  the  soap  emploj'ed.  If,  then,  the  behavior  of  the  dip 
upon  dilution  is  satisfactory  (page  21)  and  indicates  the  presence  of 
sufficient  soap,  the  only  remaining  question  is  whether  there  may  be 
an  unnecessary  and  possibly  harmful  amount  of  alkali  present.  In 
the  presence  of  the  large  amount  of  cresylic  acid  contained  in  these 
dips  there  can  be,  strictly  speaking,  no  "  free  alkali."  The  ideal 
cresol  dip  will,  however,  unquestionably  contain  no  alkali  above  that 
necessary  to  obtain  complete  saponification  of  the  linseed  oil.  An 
excess  of  alkali  can  be  of  no  possible  benefit  and  might  conceivably  be 
undesirable  for  several  reasons.  A  useful  test  for  the  presence  of 
such  an  excess  of  alkali  is  that  of  Kelhofer.^ 

Ten  grams  of  dip  is  thoroughly  shaken  in  a  small  separatory  funnel 
with  50  c,  c.  of  a  saturated  solution  of  XaCl.  After  complete  sepa- 
ration has  taken  place  the  lower  aqueous  layer  is  removed,  diluted 
with  an  equal  volume  of  water,  and  a  few  drops  of  phenolphthalein 
added.  If  the  dip  has  been  made  from  a  perfectly  neutral  linseed- 
oil  soap,  there  will  appear  at  most  but  a  slight  reddening  of  the  solu- 
tion, which  vanishes  upon  the  addition  of  a  drop  of  half-normal 
acid.  If  more  acid  is  required  to  remove  the  pink  color,  the  pres- 
ence of  an  excess  of  alkali  is  indicated.  The  test  can  not  be  made 
quantitative,  for  experiments  have  shown  that  only  a  part  of  the 
excess  of  alkali  actually  present  is  accounted  for  in  this  way,  the 
remainder  probably  being  thrown  up  in  the  form  of  alkali  cresylate 
into  the  upper  layer  with  the  soap.  It  would  seem,  then,  reasonable 
to  demand  that  no  dip  treated  as  described  should  require  more  than 
a  very  few  tenths  of  a  cubic  centimeter  of  half-normal  acid  to  remove 
the  pink  color  imparted  by  phenolphthalein  to  the  sodium  chlorid 
extract. 

<*  I^vvkowitscb,  J.,  Chemical  Technology  and  Analysis  of  Oils,  Fats,  and 
Waxes,  ;id  ed.,  Vol.  I,  p.  '.iM.     KMM. 

'I  Schweizerische  Wochenschrlft  fiir  Cheniio  nnd  riiarniazir,  jalirj?.  4(1,  No.  2, 
pp.  ir>-20.    Znrich,  Jan.  11,  1!IU8. 


24  ANALYSIS   OF   COAL-TAR   SHEEP  DTPS. 

Duyk  "  proposes  a  method  for  the  determination  of  soap  in  cresol 
dips,  according  to  which  the  soap  is  separated  by  shaking  the  dip 
with  a  strong  sugar  sohition.  The  latter  dissolves  all  the  soap,  which 
may  be  recovered  by  salting  out  with  NaCl,  and  purified,  if  desired, 
by  solution  in  alcohol.  The  method  has  not  been  tried  in  this 
laboratory. 

ANALYSIS  OF  COAL-TAR  OILS  AND  COMMERCIAL  CRESYLIC  ACID. 

Obviously  it  is  impossible  for  a  numufacturer  to  produce  a  dip  of 
constant  composition  closely  adhering  to  the  standard  he  has  set  for 
himself  in  his  original  sample  submitted  to  the  Department  of  Agri- 
culture for  examination  unless  he  knows  exactly  what  goes  into  each 
lot  of  dip  his  factory  turns  out.  The  composition  of  coal-tar  oils  is 
subject  to  considerable  variation ;  consequently  it  is  absolutely  neces- 
sary for  any  manufacturer  who  wishes  to  secure  and  retain  permis- 
sion for  the  use  of  his  dip  in  official  dipping  to  have  at  his  disposal 
some  means  of  accurately  analyzing  each  lot  of  coal-tar  oils  he  re- 
ceives. He  may  then  blend  his  oils,  or  his  oils  and  cresylic  acid,  in 
such  proportions  as  always  to  preserve  uniform  the  composition  of 
his  dip. 

The  coal-tar  oils  to  be  used  for  dips  nnist  be  examined  for  water, 
pyridin  bases,  and  phenols. 

Water  will  be  determined  exactly  as  in  dips  (page  10). 

Pyridin  bases  will  be  determined  exactly  as  in  dips  (page  11),  but 
if  the  oils  are  old  and  highly  colored  it  may  prove  advantageous  to 
use  5  grams  instead  of  10. 

The  hope  was  entertained  that  phenols  in  coal-tar  oils  and  cresylic 
acid  might  be  readily  and  accurately  estimated  by  dissolving  a 
weighed  amount  in  benzol,  shaking  with  acidified  aqueous  sodium 
sulphate  to  remove  water,  and  then  shaking  the  separated  benzol 
solution  in  the  measuring  tube  with  caustic  soda;  in  short,  by  repeat- 
ing exactly  the  last  two  steps  of  the  method  employed  for  phenols  in 
dips.  In  fact,  the  latter  was  adopted  for  dips  with  considerable 
added  satisfaction  because  it  seemed  to  promise  an  easy  solution  of 
one  of  the  most  troublesome  problems  of  dip  making  by  affording 
such  a  simple  means  for  valuing  coal-tar  oils,  requiring  no  special 
technical  training  for  its  execution,  and  yet  being  a  method  strictly 
parallel  in  all  respects  to  the  method  employed  in  analyzing  the  com- 
pleted dip. 

This  hope  was  not  realized,  for  it  was  found  that  some  samples 
at  any  rate  of  creosote  oils  and  of  cresylic  acid  contain  small  amounts 
of  acid  bodies  of  some  description,  possibly  phenoloids,  possibly  of  a 
resinous  nature,  which  are  taken  up  by  caustic  soda,  increasing  its 

oAunales  de  Clilmie  Analytique,  1. 12,  No.  9,  pp.  345-346.    Paris,  Sept.  15. 1907. 


CALCULATIOlSr   OF  PROPER  DILUTION   OF   DIPS.  25 

A'olume,  but  which  are  not  volatile  with  steam.  There  seems  to  be 
no  way  of  determining  these  bodies  in  the  dip,  provided  they  are 
phenoloids ;  hence  it  seems  necessary  to  define  cresylic  acid  within  the 
scope  of  the  regulations  as  "  phenols  derived  from  coal  tar,  none  of 
which  boils  below  185°  C.  nor  above  250°  C,"  and  which  are  com- 
pletely volatile  with  steam  at  100°  C.  The  only  resource,  accordingly, 
is  to  handle  the  oils  and  cresylic  acid  in  exactly  the  same  way  as  the 
dips  themselves  are  handled  (page  13),  by  distillation  of  an  appro- 
priate weight  of  the  acidified  oil  in  a  current  of  steam,  with  the  sub- 
sequent extractions  and  measurement  as  described. 

As  might  be  expected,  cresylic  acid  appears  to  contain  a  smaller 
per  cent  of  these  acid  bodies  not  volatile  wit-h  steam  than  does  creo- 
sote oil.  Very  probably  the  amount  is  subject  to  considerable  varia- 
tion in  different  samples.  Results  on  certain  samples  will  be  given 
in  the  section  on  experimental  work  (page  33). 

CALCULATION   OF  PROPER  DILUTION   OF   DIPS. 
COAL-TAR  CREOSOTE  DIPS. 

The  regulations  of  the  Secretary  of  Agriculture "  state  that  a 
coal-tar  creosote  dip  "  should  contain  when  diluted  ready  for  use 
not  less  than  1  per  cent  by  weight  of  coal-tar  oils  and  cresylic  acid. 
In  no  case  should  the  diluted  dip  contain  more  than  four-tenths  of 
1  per  cent  nor  less  than  one-tenth  of  1  per  cent  of  cresylic  acid; 
but  when  the  proportion  of  cresylic  acid  falls  below  two-tenths  of 
1  per  cent  the  coal-tar  oils  should  be  increased  sufficiently  to  bring 
the  total  of  the  tar  oils  and  the  cresylic  acid  in  the  diluted  dip  up  to 
1.2  per  cent  by  weight." 

In  calculating  from  the  composition  of  a  dip  its  proper  dilution 
under  this  regulation  three  points  must  be  borne  in  mind.  First, 
the  regulations  demand  that  hydrocarbons  and  phenols  must  be 
present  in  certain  minimum  percentages  by  weight,  whereas  in  prac- 
tice a  dip  is  always  diluted  by  volume.  Second,  the  regulations 
set  two  independent  minimum  pairs  of  values  below  which  the  per- 
centages of  phenols  and  of  hydrocarbons  and  phenols  may  not  fall, 
though  they  may  rise  above  these  set  values  within  certain  liuiits, 
thus  allowing  a  considerable  range  in  the  possible  composition  of 
a  dip.  Third,  the  calculated  dilution  uiust  be  the  greatest  possible 
dilution  which  the  dip  under  consideration  can  obtain  under  the 
regulations. 

Three  steps  will  then  be  involved  in  the  calculation  of  the  dilu- 
tion of  a  coal-tar  creosote  dip,  (1)  The  selection  of  the  pair  of 
minimum  percentages  of  phenols  and  of  hydrocarbons  and  phenols 

"  IJiireau  of  Animal  Industry  Order  14.'i.  page  18. 


26  ANALYSIS  OF  COAL-TAR  SHEEP  DIPS. 

most  advantajreous  for  tliat  particular  dip;  (2)  the  calculation  of 
the  niaxiinum  dilution  by  wei<i:ht  which  a  dip  of  that  composition 
can  be  trranted  under  the  section  of  the  rej^ulation  most  advan- 
tageous to  it;  (3)  by  employment  of  the  specific  jnrravity  of  the  dip 
as  a  factor  to  pass  from  the  obtained  maximum  dilution  by  weight 
to  the  maximum  dilution  by  volume. 

These  data  having  been  thus  fully  set  forth,  it  hardly  seems  neces- 
sary to  enter  into  the  actual  solution  of  the  problem,  since  the  matter 
is  purely  one  of  nuithenuitics.  It  will  be  sufficient  to  state  that  a 
mathematical  analysis  of  the  above  regulation  will  lead  to  the  fol- 
lowing four  cases  and  the  four  corresponding  rules  for  obtaining 
the  maximum  dilution  in  each  case: 

Case  I. — When  the  percentage  of  phenols  is  less  than  (me-twelfth 
of  the  sum  of  the  percentages  of  hydrocarbons  and  phenols. 

IJule:  Multiply  the  percentage  of  phenols  by  10,  subtract  1  from 
the  product,  and  multiply  the  remainder  by  the  specific  gravity  of 
the  dip. 

The  diluted  dip  will  then  contain  0.1  per  cent  phenols  and  over  1.2 
per  cent  hydrocarbons  and  phenols. 

Ca.se  II. — When  the  j^ercentage  of  phenols  is  between  one-twelfth 
and  one-sixth  of  the  sum  of  the  percentages  of  hydrocarbons  and 
phenols. 

Rule:  Divide  the  sum  of  the  percentages  of  hydi'ocarbons  and  phe- 
nols by  1.2,  subtract  1  from  the  quotient,  and  multiply  the  remainder 
by  the  specific  gravity  of  the  dip. 

The  diluted  dip  will  then  contain  1.2  per  cent  of  hydrocarbons  and 
phenols  and  between  0.1  and  0.2  per  cent  of  phenols. 

Case  III. — When  the  percentage  of  phenols  is  between  one-sixth 
and  one-fifth  of  the  sum  of  the  percentages  of  hydrocarbons  and  phe- 
nols. 

Rule:  Multiply  the  percentage  of  phenols  by  5,  subtract  1  from 
the  product,  and  ipultiply  the  remainder  by  the  specific  gravity  of 
the  dip. 

The  diluted  dip  will  then  contain  0.2  per  cent  phenols  and  between 
1  and  1.2  per  cent  hydrocarbons  and  phenols. 

Case  IV. — When  the  percentage  of  phenols  is  between  one-fifth 
and  two-fifths  of  the  sum  of  the  percentages  of  hydrocarbons  and 
phenols. 

Rule :  Subtract  1  from  the  sum  of  the  percentages  of  hydrocarbons 
and  phenols,  and  multiply  the  remainder  by  the  specific  gravity  of 
the  dip. 

The  diluted  dip  will  then  contain  1  per  cent  hydrocarbons  and  phe- 
nols and  between  0.2  per  cent  and  0.4  per  cent  of  phenols. 

In  each  case  the  result  obtained  by  the  rule  is  the  number  of  parts 
by  volume  which  may  be  added  to  one  part  by  volume  of  the  dip ;  in 


EXPERIMENTAL   WORK   WITH    METHODS   OF  ANALYSIS. 


27 


practice,  the  greatest  number  of  gallons  of  water  which  may  be  added 
to  one  gallon  of  dip. 

It  may  be  stated  that  if  the  percentage  of  phenols  is  greater  than 
two-fifths  of  the  sum  of  the  percentages  of  hydrocarbons  and  phenols, 
the  use  of  the  dip  can  not  be  permitted  under  the  regulations,  for 
when  diluted  until  it  contains  1  per  cent  of  hydrocarbons  plus  phenols, 
the  minimum  allowed,  it  will  necessarily  contain  above  0.4  per  cent  of 
phenols,  which  amount  is  set  as  the  maximum  limit. 

CRESYLIC-ACID  DIPS. 

The  aforementioned  regulations  state  in  regard  to  the  cresol  dip 
that  "  when  diluted  ready  for  use  this  dip  should  contain  one-half 
of  1  per  cent  of  cresylic  acid."  From  this  may  be  derived  the  rule : 
Multiply  the  percentage  of  phenols  by  2,  subtract  1  from  the  product, 
and  multiply  the  remainder  by  the  specific  gravity  of  the  dip. 

EXPERIMENTAL  WORK  WITH  METHODS  OF  ANALYSIS. 

Much  experimental  work  was  done  in  developing  and  testing  the 
previously  described  methods  of  analysis.  A  brief  outline  of  some 
of  this  experimental  work,  with  a  more  detailed  discussion  of  certain 
results,  may  be  of  interest. 

DETERMINATION   OF   PHENOLS. 

Particular  difficulty  was  experienced  Avith  phenols.  It  early  be- 
came clear  that  the  most  desirable  method  of  finally  estimating  their 
amount  would  be  by  measuring  the  increase  of  volume  shown  by  a 
solution  of  caustic  soda  when  the  phenols  in  question  were  absorbed 
by  it.  The  general  reasons  for  this  conclusion  have  already  been 
discussed.    Attention  will  now  be  paid  to  some  special  points  involved. 

I.  When  weighed  amounts  of  pure  phenols  are  shaken  in  the  meas- 

weiffht  phenols 
uring  tube  as  described,  and  the  coefficient      volume  increase  NaOH 

determined,  it  was  found  that — 

(«)  This  coefficient  is  constant  for  a  given  phenol  irrespective  of 
the  amount  measured — within  the  limits  of  the  tube — and  of  the 
presence  or  absence  of  other  coal-tar  hydrocarbons  in  addition  to 
benzol.  To  illustrate,  weighed  amounts  of  a  fairly  pure  cresylic  acid 
were  dissolved  in  benzol  and  sliaken  in  the  measuring  tube  with 
caustic  soda,  with  the  following  results: 


Weight  of 

Increa.se  in 

cresol. 

volume  of 

NiiOH. 

Cubic  cen- 

Grams. 

timeters. 

9.1386 

8.66 

9.  '282.5 

8.62 

9.6160 

8.82 

2. 3893 

2.22 

2. 3228 

2.19 

Coefficient: 

(weight  phenol.s         \ 
volunje  increii.se  NaOH./ 


1.055 
1.078 
1.079 
1.07ii 
1.060 


28  ANALYSIS   OF   COAL-TAR   SHEEP   DIPS. 

Althoufjh  approximately  four  times  as  much  cresol  was  employed 
in  the  first  three  trials  as  in  the  last  two,  the  derived  coefficient  is 
practically  identical. 

(b)  This  coefficient  is  not  the  same  for  all  phenols,  but  varies  in 
the  same  direction  as  the  specific  gravity  of  different  phenols,  though 
in  greater  ratio,  accordingly  varying  inversely  as  the  molecular 
weights  of  the  different  phenols  and  in  approximately  equal  inverse 
ratio.  For  the  mixtures  of  phenols  ordinarily  occurring  in  commer- 
cial cresylic  acid  and  in  the  grades  of  coal-tar  creosote  oils  commonly 
used  for  making  dips,  the  average  coefficient  proved  to  be  unity  as 
nearly  as  could  he  determined. 

II.  When  weighed  amounts  of  pure  phenols  were  shaken  in  a 
separatory  funnel  with  water,  soda,  sulphuric  acid,  and  benzol  in 
the  proportions  described  in  the  analytical  method,  and  the  phenols 
then  brought  to  measurement,  the  coefficients  in  all  cases  were  found 
to  run  parallel  to  those  obtained  in  Experiment  I,  but  to  be  very 
slightly  lower;  that  is,  water  is  carried  by  the  phenols  into  benzol 
solution  in  amount  rather  more  than  enough  to  balance  the  amount 
of  phenols  retained  by  the  acid  aqueous  layer  in  the  separatory 
funnel.     No  loss  is  therefore  here  involved. 

III.  The  validity  of  the  method  of  measurement  having  been  thus 
established,  the  next  problem  was  to  concentrate  without  loss  of 
phenols  the  large  volume  of  distillate  resulting  from  the  distillation 
of  the  acidified  dip  with  steam  to  a  volume  sufficiently  small  to  be 
introduced  into  the  measuring  tube. 

(a)  The  first  attempt  was  concentration  by  evaporation  of  the 
liquid  after  rendering  it  strongly  alkaline.  Weighed  amounts  of 
phenols  were  dissolved  in  800  c.  c.  of  water  and  25  c.  c.  of  caustic 
soda  1 : 3,  and  evaporated  to  40  to  50  c.  c.  on  the  steam  bath,  and  the 
phenols  were  then  separated  and  brought  to  measurement  as  de- 
scribed. It  was  found  that  this  proceeding  involved  a  loss  averaging 
at  least  5  per  cent,  the  percentage  increasing  as  the  molecular  weights 
of  the  phenols  increased.  This  result  could  be  expected,  for  the 
higher  phenols,  being  of  much  less  solubility  in  dilute  caustic  soda, 
and  being  more  weakly  acid  and  their  salts  consequently  more  easily 
hydrolyzed,  would  naturally  suffer  a  greater  percentage  of  loss  than 
the  lower,  more  acid  phenols. 

(h)  An  attempt  was  next  made  to  extract  phenols  from  the  dis- 
tillate with  benzol,  then  concentrate  the  benzol  solution  by  distillation 
to  a  residual  quantity  of  about  60  c.  c,  which  was  lastly  brought 
into  the  measuring  tube  with  caustic  soda.  Weighed  amounts  of 
phenols  were  brought  into  a  1,500  c.  c.  separatory  funnel  with  800 
c.  c.  of  water,  and  shaken  with  benzol  in  the  amount  and  manner 
described  in  the  analytical  method  (page  15),  both  with  and  with- 
out the  addition  of  NaCl.  Without  addition  of  XaCl  each  extrac- 
tion with  benzol  removes  at  most  but  75  per  cent  of  the  phenol 


EXPERIMENTS   IN   DETERMINING  PHENOLS. 


29 


present  each  time;  with  12|  grams  NaCl  per  100  c.  c.  about  87  per 
cent  is  withdrawn,  and  with  25  grams  per  100  c.  c,  between  92  and 
94  per  cent  is  taken  up  by  the  benzol  in  each  extraction.  Three 
extractions  as  described  will  therefore  account  for  99.95  per  cent 
of  the  amount  of  phenols  originally  present.  This  was  eminently 
satisfactory.  But  when  the  benzol  extract  was  submitted  to  distilla- 
tion, variable  amounts  of  phenols  were  found  in  the  distillate,  the 
amount  being  almost  negligible  in  the  case  of  phenols  of  high  boil- 
ing point,  but  considerable  with  the  lower  phenols,  and  especially 
notable  in  the  case  of  benzophenol. 

(c)  Attempt  was  next  made  to  hold  back  phenols  while  benzol 
was  being  distilled  as  described  in  (Z>),  by  the  addition  of  a  few 
grams  of  metallic  sodium,  the  idea  being  to  eliminate  the  effect  of 
small  amounts  of  water  and  at  the  same  time  to  bring  the  phenols 
into  a  completely  nonvolatile  compound.  This  attempt  was  quickh^ 
abandoned,  for  the  reaction  between  sodium  and  phenols  proved 
very  slow  and  incomplete,  even  on  long  standing  or  boiling  with 
reflux  condenser. 

{d)  It  will  be  noted  that  high-boiling  phenols  suffer  special  loss 
by  the  method  of  (a)  and  low-boiling  phenols  by  method  (h),  while 
the  method  of  extraction  of  (b)  is  perfectly  adequate.  Therefore 
an  attempt  was  made  to  combine  the  two  methods  by  distilling  off 
the  benzol  over  strong  caustic  soda — 15  c.  c.  of  1 :  2  NaOH — the  idea 
being  that  the  strong  caustic  soda  would  hold  nearly  all  the  phenols 
in  combination,  and  afford  on  account  of  its  concentration  but  slight 
opportunity  for  hj'drolysis  and  formation  of  water  vapor,  while 
since  those  very  phenols  most  subject  to  hydrolysis  and  loss  from 
the  caustic  soda  are  those  of  high  boiling  point  and  but  slight  vola- 
tility with  vapors  of  benzol,  practically  no  appreciable  amount  of 
phenols  would  escape  from  the  flask.  This  proved  to  be  the  case. 
Delicate  qualitative  tests  show  the  presence  of  phenols  in  the  dis- 
tillate, but  in  amount  far  beyond  the  power  of  the  measuring  tube 
to  detect. 

The  following  table  will  illustrate  some  of  the  positive  points 
brought  out  in  Experiments  I,  II,  and  III.  Purified  cresol  was 
employed,  obtained  in  the  laboratory  from  crude  cresylic  acid. 

Results  of  experiments  upon  the  method  for  determining  phenols. 


Method  of  treatment. 


Dissolved  in  benzol  and  shaken  with  NaOH 
in  tube 

In  separatory  funnel  with  benzol,  NaOH, 
and  H2SO4,  then  as  in  analysis 

With  800  c.  c.  water,  200  g.  NaCl.  then 
treated  as  in  analysis 


Weight    Increase  of 
taken.        NaOH. 


Grams. 
6.855 

7.542 
7.773 
8.433 
9.776 
9.344 


j       CuMc 

I  cciili meters. 
6.69 
8.50 
7.52 
7.75 
8.30 
9.81 
9.40 


CoelBcient: 
weight  phenols       \l 
volume  increase  NaOH./ 


1.023 
1.015 
1.003 
1.003 
1.016 
.997 
.998 


Mean  co- 
efficient. 


1.019 


80 


ANALYSIS   OF   COAL-TAR   SHEEP  DIPS. 


It  is  evident,  accordingly,  that  the  method  described  will  bring  to 
measinvnu'iit,  with  no  loss,  all  the  phenols  present  in  the  distillate 
from  the  dip. 

TKSTS   WITH  COAL-TAR  CREOSOTE  DIPS  OF  KNOWN   COMPOSITION. 

The  next  undertaking  was  to  make  up  a  coal-tar  creosote  dip  of 
accurately  known  composition  in  order  to  test  upon  it  the  validity 
in  practice  of  the  methods  of  analysis  developed. 

Dip  No.  1. — Rosin :  A  fair  grade  of  ordinary  commercial  rosin  was 
emj)loyed.    Weight  used,  220  grams. 

Hydrocarbons:  Coal-tar  oils,  supposed  to  be  free  from  phenols, 
shaken  four  times  with  10  to  25  per  cent  caustic  soda,  dried  over 
calcium  chlorid,  and  filtei-ed.    Weight  taken,  550  grams. 

Pure  phenols:  Obtained  by  the  purification  in  the  laboratory  of 
crude  cresylic  acid.    Weight  taken,  120  grams. 

Caustic  soda  and  water:  One  part  pure  NaOH  dissolved  in  two 
parts  water.  By  titration  with  N/2  H.SO4  and  methyl  orange  the 
solution  showed  24.7  per  cent  Na.O  and  75.30  j^er  cent  water. 
Amount  taken,  00  grams,  which  accordingly  contained  00  X  0.247  = 
22.23  grams  Na^O  and  00  X  0.753  ==  C7.77  grams  water.  There  was 
also  added  20  c.  c.  water,  making  the  total  water  used  87.77  grams. 

The  dip  accordingly  contained : 


Grams. 

Per  cent. 

Water - 

Soda  (NasO) 

87.77 
22.23 
220.00 
120.00 
550.00 

8.78 
2.22 
22.00 
12.00 
55.00 

Rosin 

Phenols 

Hydrocarbons  and  pyridin-  

1,000.00 

100.00 

Saponification  was  effected  in  a  flask  connected  with  a  reflux  con- 
denser and  immer.sed  in  a  water  bath. 
Analysis  of  dip  No.  1  gave : 


Water 

Soda- 

Pyridin 

Phenols 

Rosin  acids,  gravimetric 

Rosin  apids,  volumetric. 


A. 

B. 

Percent. 

Per  cent. 

8.8 

8.6 

2.15 

2.17 

1.19 

1.90 

11.78 

11.74 

19.90 

19.80 

Ul)20.03 

(1)19.94 

{(2)19.97 

(2)19.81 

Mean. 


Per  cent. 

8.7 
2.16 
1.25 
11.76 
19.85 

\        19.94 


It  will  be  noted  that,  as  was  to  be  expected,  the  amount  of  rosin 
acids  found  is  about  00  per  cent  of  the  rosin  used  in  the  dip.  The 
results  seemed  very  satisfactory,  except  perhaps  in  the  case  of  the 
phenols.     (But  see  page  35.) 


TESTS   WITH   COAL-TAR  DIPS   OF   KNOWN   COMPOSITION. 


31 


Dip  No.  2. — ^Made  up  more  as  a  dip  would  be  made  in  practice. 
Rosin,  200  grams. 

Coal-tar  oils  which  were  used  gave  on  analysis : 


A. 

B. 

Mean. 

Water ... 

Per  cent. 
0.40 
3.35 
20.30 
75.95 

Percent. 
0.50 
3.56 
20.40 
75. &i 

Per  cent. 
0.45 

Pyridin .  .      .    

3.45 

Phenols.  -.-        _        _          .... 

20.35 

Hydrocarbons,  by  diflference.  .    .      . ..  .    _. 

75.75 

100.00 

100.00 

100.00 

Amount  taken,  700  grams,  which  would  give: 

Grams. 

Water 700X0.0045=     3.15 

Pyiidiu 700X   .0345=  24.15 

Phenols    700X   .2035=142.45 

Hydrocarbons 700X   .7575=530.25 

Soda  and  water:  By  titration  with  X/2  H^SO^  and  methyl  orange 
the  solution  was  found  to  contain  25.22  per  cent  NagO  and  74.78  per 
cent  HgO.  Ninety  grams  of  the  solution  were  employed,  giving  22.7 
grams  Na^O  and  G7.3  grams  H^O.  There  was  also  added  10  c.  c.  of 
water.  The  materials  were  all  put  together  in  a  1,500  c.  c.  flask  and 
the  latter  was  stoppered  and  shaken  frequently  until  saponification 
was  complete,  with  application  of  no  external  heat. 

The  dip  accordingly  contained: 

Per  cent. 

Water    ( 0.32-1- 6.73 -h  1.0) S.  05 

Soda    (Na^O) 2.27 

Pyridin 2.42 

Rosin 20.00 

Phenols 14.  25 

Coal-tar  hydrocarbons 53.01 

Total 100.00 

Analysis  gave  the  following  results: 


A. 

B. 

Mean. 

Water.    .          .  .       „ .- 

Per  cent. 
8.10 
2.28 
2.28 
"18.66 
14.16 
'      .'>4.52 

Tercent. 
8.30 
2.26 
2  ''1 

"liiso 

14.06 
54.37 

Percent. 
8.20 

Soda .. 

2.27 

Pyridin - 

2.25 

18.73 

14.11 

54.44 

100.00 

100.00 

100.00 

'  Volumetrlp. 


*  Gravimetric. 


Results  from  this  dip  ai)pear  very  satisfactory.  It  sliould  be  noted 
that  the  formuhis  employed  in  the  experimental  dips  are  in  no  way 
recommended  for  a(;tual  use.  The  immediate  object  was  not  to  make 
a  superior  dip,  but  merely  to  test  the  methods  of  analysis  employed. 


32  ANALYSIS   OF   COAL-TAR   SHEEP  DIPS. 

TEST   WITH    CRESYLIC    ACID   DIP   OK    KNOWN    COMPOSITION. 

The  next  experiments  were  to  test  in  the  same  way  the  validity  of 
the  methods  when  applied  to  cresylic  acid  dips.  Dip  No.  :i  was  ae- 
cordin<^ly  made  somewhat  along  the  lines  of  the  U.  S.  P.  formula  for 
liquor  cresolis  compositus. 

One  hundred  and  seventy-five  grams  of  linseed  oil  was  saponified 
in  a  beaker  with  81  grams  of  a  solution  of  pure  KOH,  shown  by  titra- 
tion with  N/2  1X2804  and  methyl  orange  to  contain  35.9  per  cent  of 
K/)  and  i'A.l  per  cent  H2O.  Accordingly  8lX0.:i59=21).08  grams 
K2O,  and  81X0.041  =  51.92  grams  H^O  were  introduced.  The  beaker 
with  its  contents  was  weighed  before  and  again  after  saponification, 
and  a  loss  of  8.5  grams  noted,  leaving  in  the  soap  finally  51.92—3.5=: 
48.42  gi'ains  of  ILO.    The  materials  employed  in  the  soap  were  then — 

Grams. 

Linseed  oil 175.00 

Potasli    (K=0)    29.08 

Water 48.42 

Total 252.  5 

Now,  taking  as  the  mean  molecular  weight  of  the  fat  acids  of  lin- 
seed oil  the  number  284.7,"  and  as  the  molecular  weight  of  glycerin 
the  number  92,  the  mean  molecular  weight  of  linseed  oil  will  be 
3 (284.7) +92— 54=892.1.  The  175  grams  of  linseed  oil  will  then  be 
equivalent  to — 

92 
Glycerin,  175  X;jrr-T= 18.03  grams. 

854—27 
Fatty  acid  anhydrids,  175  X  =162.25  grams. 

54 
But  this  glycerin  will  take  up  18. 03 X r-^,  =5.28  grams  H^O  in  the 

process  of  saponification  of  the  linseed  oil,  hence  the  completed  soap 
theoretically  consists  of — 

Grains. 

Glycerin 18.03 

Fatty  acid  anhydrids 162.25 

K2O 29.  08 

Water  (48.42—5.28) 43.14 

Total -._ 252.50 

The  soap  was  transferred  to  a  tared  liter  flask  with  the  aid  of 
U.  S.  P.  cresylic  acid  (cresylic  acid  from  two  different  manufac- 
turers being  mixed  in  equal  parts  to  secure  a  fair  sample),  the  con- 
tents were  brought  to  500  grams  with  cresylic  acid,  and  the  flask 
was  .stoppered  and  frequently  shaken  for  several  days  till  a  uniform, 

°  I^nvkowitscli,  .7.  Chemical  Technology  and  Analysis  of  Oils,  Fats,  and 
Waxes,  3d  Ed.,  vol.  1,  p.  334.    1904. 


TEST   WITH  CRESYLIC  ACID  DIP  OF  KNOWN   COMPOSITION.        33 

clear  liquid  resulted.  The  mean  of  four  analyses  (page  34)  showed 
the  U.  S.  P.  cresol  employed  to  be  98.80  per  cent  pure.  The  amount 
used  was  500 — 252.5=247.5  grams,  containing  accordingly  247.5X 
0.988=244.53  grams  phenols  and  247.5X0.012=2.97  grams  of  pyri- 
din,  hydrocarbons,  etc. 

Analysis  of  the  dip  ought  then  to  show : 

Per  cent. 

Water 8.  63 

K2O 5.  82 

Fatty  acid  anhydrids -_ 32.45 

Glycerin 3.  61 

Phenols 48.90 

Pyridin,  hydrocarbons,  etc 0.59 

Total 100. 00 

Actual  analysis  of  this  dip  gave  the  following  results : 


A. 


Water 

K2O 

Fatty  acid  anhydrids- 

Glycerin 

Phenols 

Pyridin 


B.       Mean. 


8.1 

8.0 

8.05 

5.71 

5.72 

5.71 

31.50 

31.39 

31.45 

3.50 

3.49 

3.50 

48.77 

48.98 

48.88 

0.28 

0.28 

0.28 

TESTS    FOR    NONVOLATILE    ACID    UODIES    IN    COAL-TAR    CREOSOTE    AND    COM- 
MERCIAL CRESYLIC  ACID. 

Mention  has  already  been  made  of  the  fact  (page  24)  that  both  coal- 
tar  oils  and  commercial  cresylic  acid  may  contain  bodies  of  an  acid 
nature,  absorbed  by  caustic  soda  solution  with  a  consequent  increase 
in  its  volume,  but  which  are  not  volatile  with  steam  at  100°  C.  These 
acid  bodies  very  probably  vaiy  in  amount  in  different  samples  of  oils 
and  cresols,  and  may  not  be  present  in  every  case.  Examinations 
were  made  of  the  coal-tar  creosote  oil  employed  in  making  dip  No.  2, 
and  of  the  U.  S.  P.  cresol  used  in  dip  Xo.  3. 

The  coal-tar  creosote  oil  used  in  preparing  dip  Xo.  2  was  found  to 
contain  by  distillation  of  the  oil  with  steam  20.35  per  cent  phenols,  as 
the  mean  of  the  two  results  20.30  per  cent  and  20.40  per  cent.  The 
oils  were  then  handled  in  another  way,  namely,  100  grams  were  dis- 
tilled from  an  Engel  flask  to  300°  C.  The  first  portion  of  the  distil- 
late containing  water  was  received  in  a  small  stoppered  cylinder,  ben- 
zol and  XaCl  were  added,  the  cylinder  was  shaken,  and  after  .separa- 
tion had  taken  place  the  benzol  was  pipetted  out  and  added  to  the  rest 
of  the  distillate.  Extraction  of  the  aqueous  portion  was  repeated 
several  times  in  the  same  way.  The  total  oily  distillate  was  made  to 
a  definite  volume  with  benzol,  an  aliquot  part  shaken  with  caustic 
soda  in  the  measuring  tube  and  the  increase  in  volume  noted.     Some- 


34 


ANALYSIS  OF  COAL-TAR  SHEEP  DIPS. 


what  variable  re.sults  were  obtained,  ranj^ing  between  21.80  and  23.20 
for  the  per  cent  of  phenol.s  found  by  this  method  in  the  creosote  oil. 

In  the  examination  of  the  U.  S.  P.  cresol  used  in  dip  No.  3  weighed 
amounts  of  the  cresol  were  introduced  into  a  150  c.  c.  separatory  fun- 
nel, with  15  c.  c.  of  1 : 2  XaOH  and  30  to  40  c.  c.  Avater,  then  benzol 
and  H.SO^  added,  and,  in  short,  the  last  two  steps  of  the  adopted 
analytical  method  were  followed  in  detail  until  the  phenols  were 
brought  to  measurement. 

Treated  in  this  way  9.059  grams  cresol  gave  9.13  c.  c.  increase  in 
volume  of  XaOH=  100.77  per  cent  phenols;  8.146  grams  cresol  gave 
8.15  c.  c.  increase  in  volume  of  NaOH=  100.05  per  cent  phenols.  The 
U.  S.  P.  cresol  will  then  appear  by  this  method  to  contain  100.41  per 
cent  phenols,  the  mean  of  the  two  results  obtained. 

Phenols  were  now  determined  exactly  as  they  would  be  in  a  dip, 
by  steam  distillation  of  weighed  amounts  of  the  U.  S.  P.  cresol. 


Weight 
cresol. 

Increase 

in  volume 

NaOH. 

Per  cent 
phenols. 

Orams. 
9.457 
9.590 
9.468 
9.105 

Grams. 
9.40 
9.46 
9.36 
8.95 

99.40 
96.64 
96.86 
-98.30 

The  mean  of  these  results  is  98.80  per  cent,  while  the  range  of  dif- 
ference between  the  results  is  about  1  per  cent  of  the  amount  of 
plienols  operated  upon.  AMien  working  with  nearly  pure  phenols  it 
is  difficult  to  obtain  results  which  check  as  closely  as  desirable,  for 
the  meniscus  is  subject  to  considerable  variation  in  shape  and  degree 
of  curvature.  This  variation  in  the  form  of  the  meniscus  appears  to 
a  less  extent  when  the  phenols  from  a  cresol  dip  are  measured,  and 
is  practically  absent  in  case  the  phenols  have  been  obtained  from  a 
creosote  dip,  hence  readings  in  these  cases  check  more  closely.  lai 
practice  results  may  reasonably  be  expected  to  check  within  this 
limit  of  1  per  cent  of  the  total  amount  of  phenols  in  all  cases ;  that  is, 
results  on  a  cresol  dip  containing  50  per  cent  phenols  agree  within 
0.5  per  cent,  and  those  on  a  creosote  dip  containing  about  10  per  cent 
phenols  within  0.1  per  cent. 

It  is  accordingly  evident  that  both  coal-tar  creosote  oils  and  even 
quite  pure  cresylic  acid  may  contain  bodies  of  an  acid  nature,  which 
may  possibly  be  phenoloids,  but  for  the  determination  of  which, 
since  they  are  not  volatile  with  steam,  there  appears  at  present  no 
possible  means.  In  the  actual  analysis  of  a  dip  these  bodies  will 
naturally  tend  to  increase  the  percentage  of  rosin  acids  found, 
whether  the  latter  are  determined  gravimetrically  or  volumetrically. 
It  is  not  likely,  however,  that  in  any  case  the  percentage  of  rosin 
acids  will  be  thus  increased  to  a  figure  greater  than  the  per  cent 


SUMMARY   OF   RESULTS.  35 

of  rosin  actually  employed  in  making  the  dip,  as  is  indicated 
by  the  result  for  rosin  acids  obtained  in  the  analysis  of  dip  Xo.  2. 
As  already  shown,  the  creosote  oil  used  in  this  dip  contained  a  consid- 
erable amount  of  nonvolatile  acid  bodies.  The  existence  of  these 
nonvolatile  acid  bodies  was  not  known  at  the  time  dip  No.  1  was 
made  and  analyzed.  Unfortunately,  no  more  of  the  purified  cresylic 
acid  used  for  that  dip  was  available  for  examination:  but  inasmuch 
as  it  was  prepared  from  a  very  crude  commercial  product,  it  undoubt- 
edly contained  an  appreciable  amount  of  these  nonvolatile  acid  bodies, 
whose  presence  may  account  for  the  somewhat  low  results  for  phenols 
obtained  in  the  analysis  of  that  dip. 

SUMMARY. 

In  conclusion  certain  points  ma}"  be  emphasized : 

1.  Methods  appear  now  available  for  determining  with  consider- 
able accuracy  the  constituents  of  coal-tar  creosote  and  cresylic  acid 
dips.  These  methods  are  not  especially  tedious,  nor,  while  requiring 
a  certain  amount  of  practice  for  their  successful  execution,  do  they 
demand  complicated  apparatus,  exceptional  skill  in  manipulation, 
or  the  liberal  use  of  expensive  chemicals.  The  results  are  all  obtained 
by  fairly  simple  volumetric  processes,  and  the  closeness  with  which 
experience  in  this  laboratory  has  shown  them  to  check,  whether  ob- 
tained by  the  same  or  different  operators,  renders  the  methods  herein 
described  particularly  adapted  to  the  standardization  of  dips. 

2.  Methods  exactly  parallel  to  the  methods  employed  in  the 
analysis  of  dips  may  be  applied  to  the  valuation  of  creosote  oil  and 
cresylic  acid  which  are  to  be  used  in  making  dips.  If  a  dip  is  prop- 
erly made  from  analyzed  materials  and  the  dip  itself  then  analyzed, 
the  actual  analysis  of  the  dip  Avill  agree  very  closely  with  its  calcu- 
lated composition.  The  validity  of  the  methods  of  analysis  is  thus 
doubly  confirmed. 

3.  Furthermore,  the  agreement  between  the  analj^sis  of  a  dip  made 
from  analyzed  materials  with  its  calculated  composition  indicates 
that  it  is  actually  possible  for  a  manufacturer  to  place  on  the  market 
a  dip  of  practically  unvarying  composition. 

O 


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